Update "Chapter 2: Using Pulsar" documentation

[Daeraxa]

Updating the "Using Pulsar" docs to remove Atom references etc and modify where necessary.

All the Atom Ch2 pages have now been added and should be working for our framework.
That means:

• Most Atom references rebranded as Pulsar
• Links to the atom repo have been replaced with pulsar-edit repo
• Some examples changes made such as the ppm search section for the packages it returns
• Links all changed to internal header links that work over the whole single index.md file.
• Pictures left untouched, we still need to have a single "theme" for redoing all our pictures of the application with atom references removed.
• Some references to apm and ATOM_HOME have been left and will be updated when these are done in core
• Some links to other chapters will not work yet and may need refactoring when those docs are included.
• Emojis for Linux🐧 , macOS🍎 and Windows🪟 will be replaced with OS correct FA6 icons once Child Theme and font awesome #62 is merged. as per Discord poll these are now replaced with LNX/MAC/WIN.

Other comments

• Wording is pretty much exactly as it was in the flight manual - this PR is not about rewording the entire documentation. This is to get these docs usable ASAP so if there are comments about wording and general refactoring then please create a PR or an issue once this has been merged.
• Comments about the "platform switching" are welcome. I've tried my best to strike a decent balance between the "tab" switcher for the different OSs (at the cost of duplicated info) which is clunky and disruptive if used too often and the "inline" key shortcuts/paths etc. (like 🐧/🪟<kbd>Ctrl+,</kbd> - 🍎<kbd>Cmd+,</kbd>) which work better when occasionally referenced in larger sections and don't cause unnecessary duplication of text.
  • These were originally handled in the flight manual by a global platform switcher and html classes which made the markdown docs messy and hard to read, we don't have a direct equivalent of this in the new docs.

This has all been tested on the main branch of this repo and works just fine in dev from what I can see but please try the links etc. in case I have missed anything or if there are any missing images due to bad references etc.

[Daeraxa]

@softcode589 I don't think you should approve draft PRs, this is only a placeholder at the moment to show that I'm working on this chapter and there are a hell of a lot of mistakes and problems still in the content. Most of the links don't work and I've not even run it on dev.

[Daeraxa]

The rest has been pushed, see the PR itself for the exact comments on this.

[Daeraxa]

As per the discord poll I've removed the emojis and replaced with three letter abbreviations (LNX/MAC/WIN).
Package website URL has been added and TODO removed for it.

@kaosine could you resolve the outdated change request?

[confused-Techie]

This PR looks good.

It's been open for quite some time without to much activity. Unless there's any final suggestions or issues to raise, I'll go ahead and merge in a bit.

As always thanks for your contributions, this was a big one

This review is outdated

[icecream17]

the commands in basic customization are already mindblowing enough that I feel the mindblown emoji ctrl+left, right change if made would be a separate pr

[confused-Techie]

I was going to initially merge this, but somehow missed this before.

The Test Deployment is failing on this PR. @Daeraxa would you be able to take a look at this?

[Daeraxa]

There was a dodgy link that I somehow missed and also didn't see the failing test for some reason.
It should be fixed now.

[confused-Techie]

Thanks for fixing those issues. With my previous approval, and tests now passing lets merge!