Prototype of getting active vscode theme in the extension

[vezwork]

The problem

As reported in #525, the visual editor does not use code highlighting colors from the user's vscode color theme.

The extension does get some colors from the theme, but it does not get any code highlighting related colors. I believe the extension includes its own code highlighting color themes for each of the default vscode themes. If the user is using a built-in vscode theme (e.g. Monokai, Solarized, etc.) then the extension is able to guess that and select a matching theme definition from its own list. However, if the user is not using a built-in vscode theme, the extension somehow picks one of the built-in themes to use as the code highlighting theme, which is not great.

You can see this maybe most glaringly with a monochrome theme from the extension store:

Source Editor with Monochromatic theme	Visual Editor with same Monochromatic theme

---

Can we get the user's theme colors?

Yes, to some extent at least. See the discussion on the vscode repo here.

This PR so far gives a prototype of getting and logging code highlighting theme data from the user's vscode theme. Here's an example of what we can get:

Here's an example of the data that is logged in this PR

'[["comment",[["foreground","#6a737d"]]],["punctuation.definition.comment",[["foreground","#6a737d"]]],["string.comment",[["foreground","#6a737d"]]],["constant",[["foreground","#005cc5"]]],["entity.name.constant",[["foreground","#005cc5"]]],["variable.other.constant",[["foreground","#005cc5"]]],["variable.language",[["foreground","#005cc5"]]],["keyword.operator.symbole",[["foreground","#000000"]]],["keyword.other.mark",[["foreground","#000000"]]],["entity",[["foreground","#6f42c1"]]],["entity.name",[["foreground","#6f42c1"]]],["variable.parameter.function",[["foreground","#000000"]]],["entity.name.tag",[["foreground","#22863a"]]],["keyword",[["foreground","#d73a49"]]],["storage",[["foreground","#d73a49"]]],["storage.type",[["foreground","#d73a49"]]],["storage.modifier.package",[["foreground","#000000"]]],["storage.modifier.import",[["foreground","#000000"]]],["storage.type.java",[["foreground","#000000"]]],["string",[["foreground","#032f62"]]],["punctuation.definition.string",[["foreground","#032f62"]]],["string punctuation.section.embedded source",[["foreground","#032f62"]]],["string.unquoted.import.ada",[]],["support",[["foreground","#005cc5"]]],["meta.property-name",[["foreground","#005cc5"]]],["variable",[["foreground","#e36209"]]],["variable.other",[["foreground","#000000"]]],["invalid.broken",[["fontStyle","bold italic underline"],["foreground","#b31d28"]]],["invalid.deprecated",[["fontStyle","bold italic underline"],["foreground","#b31d28"]]],["invalid.illegal",[["fontStyle","italic underline"],["foreground","#b31d28"]]],["carriage-return",[["fontStyle","italic underline"],["foreground","#d73a49"]]],["invalid.unimplemented",[["fontStyle","bold italic underline"],["foreground","#b31d28"]]],["message.error",[["foreground","#b31d28"]]],["string source",[["foreground","#000000"]]],["string variable",[["foreground","#005cc5"]]],["source.regexp",[["foreground","#032f62"]]],["string.regexp",[["foreground","#032f62"]]],["string.regexp.character-class",[["foreground","#032f62"]]],["string.regexp constant.character.escape",[["fontStyle","bold"],["foreground","#22863a"]]],["string.regexp source.ruby.embedded",[["foreground","#032f62"]]],["string.regexp string.regexp.arbitrary-repitition",[["foreground","#032f62"]]],["support.constant",[["foreground","#005cc5"]]],["support.variable",[["foreground","#005cc5"]]],["meta.module-reference",[["foreground","#005cc5"]]],["markup.list",[["foreground","#735c0f"]]],["markup.heading",[["fontStyle","bold"],["foreground","#005cc5"]]],["markup.heading entity.name",[["fontStyle","bold"],["foreground","#005cc5"]]],["markup.quote",[["foreground","#22863a"]]],["markup.italic",[["fontStyle","italic"],["foreground","#000000"]]],["markup.bold",[["fontStyle","bold"],["foreground","#000000"]]],["markup.raw",[["foreground","#005cc5"]]],["markup.deleted",[["foreground","#b31d28"]]],["meta.diff.header.from-file",[["foreground","#b31d28"]]],["punctuation.definition.deleted",[["foreground","#b31d28"]]],["markup.inserted",[["foreground","#22863a"]]],["meta.diff.header.to-file",[["foreground","#22863a"]]],["punctuation.definition.inserted",[["foreground","#22863a"]]],["markup.changed",[["foreground","#e36209"]]],["punctuation.definition.changed",[["foreground","#e36209"]]],["markup.ignored",[["foreground","#005cc5"]]],["markup.untracked",[["foreground","#005cc5"]]],["meta.diff.range",[["foreground","#6f42c1"],["fontStyle","bold"]]],["meta.diff.header",[["foreground","#005cc5"]]],["meta.separator",[["fontStyle","bold"],["foreground","#005cc5"]]],["meta.output",[["foreground","#005cc5"]]],["brackethighlighter.tag",[["foreground","#586069"]]],["brackethighlighter.curly",[["foreground","#586069"]]],["brackethighlighter.round",[["foreground","#586069"]]],["brackethighlighter.square",[["foreground","#586069"]]],["brackethighlighter.angle",[["foreground","#586069"]]],["brackethighlighter.quote",[["foreground","#586069"]]],["brackethighlighter.unmatched",[["foreground","#b31d28"]]],["sublimelinter.mark.error",[["foreground","#b31d28"]]],["sublimelinter.mark.warning",[["foreground","#e36209"]]],["sublimelinter.gutter-mark",[["foreground","#959da5"]]],["constant.other.reference.link",[["foreground","#032f62"],["fontStyle","underline"]]],["string.other.link",[["foreground","#032f62"],["fontStyle","underline"]]],["meta.function-call support.function",[["foreground","#005cc5"]]],["meta.function-call entity.name.function",[["foreground","#005cc5"]]],["keyword.operator",[["foreground","#000000"]]]]'