Create a new GH action to update IL baselines

[T-Gro]

The DevGuide.md file contains instructions on how to refresh IL baselines.
This involves setting an environment variable (beware of OS - specific syntax) and running a pwsh script that retrieves the actual ilverify errors and updates the baseline based on them.

All of that is described in devguide.md .

Create a new GH action that will react on comments at PRs, the command will be exactly /run ilverify.
Have a look at .github/workflows/commands.yml which contains a fantomas command that invokes formatting based on a PR comment - similar to that one, the new GH action should be ALSO placed in the same commands.yml file , it should also react to comment (/run ilverify) and it should:

• set the required environment variable
• call the pwsh script

Make sure the environment for the GH action does come with a mechanism to execute pwsh !

The name of the command shall be Update ILVerify baselines.
When executed, the command should update ilverify baselines via the script, commit and push them to the same PR (just like fantomas command does).

It will also write a comment to the PR saying how big the result git diff was:
either "The ilverify command ran and did not modify any baseline" or "The ilverify command ran and triggered following number of changes per file" - then listing each file followed by a number of lines affected.