feat: add in conditional operator sample

[bd82]

This sample is for this capability of VSCode

• https://code.visualstudio.com/api/references/when-clause-contexts#in-conditional-operator

[bd82]

@eamodio may be on interest to you as you implemented this feature in VS Code

• Add in operator support to when clauses vscode#97544

[justinmk3]

1600 lines of code to demonstrate this feature is disproportionate. The relevant lines of code in this PR only 5-10.

[bd82]

1600 lines of code to demonstrate this feature is disproportionate. The relevant lines of code in this PR only 5-10.

This PR is 1650 LOC:

• 1350 LOC are the package-lock
• 134 LOC is the extensions TS files (split into 3 files, with comments and with lots of blank lines for readability).
• The rest is sample boiler plate or sample workspace for easy of use.

The one area where the LOC can be reduced is the 134 lines of the source code.
But I wanted to produce a more meaningful example which includes:

• Two context menus, so the dynamic capabilities are emphasized.
• Highlight the need to track the state of the custom contexts (fileWatcher for change / findFiles for initial state).
• Include some basic custom logic to fill the custom contexts as the in operator is meant to allow such ext developer custom logic.

I believe a simplified sample of ~30LOC with some hard-coded values for the custom contexts
would not provide meaningful value (not really dynamic), while also not being that much easier to grok than 3 files of ~45 LOC average each...