Integrate codicons with webviews

[hoangphamEclipse]

This commit adds a reference to the codicons CSS file to enable codicons inside the TraceViewPanel of the vs-code trace extension. It follows the example provided in the vs-code webview sample.

Fixes #89.

[bhufmann]

The code seems right. However, it doesn't fix the missing icon described in #71, i.e. the filter icon is still now show.

Also, should we do the same for the other webviews (e.g. opened traces) in this project?

[hoangphamEclipse]

Hi Bernd, I tested the code on my end, I have the filter icons displayed on the DATA_TREE view mentioned in #71.

[bhufmann]

It works now when running it from the development environment using the launch configuration. However, after building the vsix (yarn vsce:package) and installing it in VsCode using install from vsix, then it doesn't work, i.e. the filter icon is not shown. I suspect that the packaging has to be adapted as well.

[hoangphamEclipse]

Looks like it is a known-issue with Codicons. You can read about it here. There is a work-around. I will try to see if that works.

[hoangphamEclipse]

Turns out the support for yarn workspace is not quite there yet for vsce package. Will continue to look for work around.

[hoangphamEclipse]

I used the copy-webpack-plugin to copy the Codicons CSS and font files automatically during the packaging process, so that they are available after the extension is packaged. The files are stored within lib/codicons. Please let me know we need to change file location.

[bhufmann]

It looks good to me. I tested with VsCode and Theia and the icons are now visible.