Feature: Automatically restart language client when config or rules files change

[StevenLove]

Especially for new users, configuring ast-grep in VSCode can be difficult because you can forget to reload the extension in which case your changes to sgconfig.yml or to your rule files will have no effect on the reported diagnostics and code actions. This PR uses vscode.workspace.FileSystemWatchers to monitor sgconfig.yml and the rules files found at ruleDirs[0] and restarts the LanguageClient when these files change. This PR includes mocha tests which verify the desired behavior and which add about 1s to npm run test

[HerringtonDarkholme]

Thanks!

[HerringtonDarkholme]

Looks like the two tests failed on Windows. Would you like to give it a look?

     1) Update on new rule creation
    2) Update on ruleDirs change back to real path

[HerringtonDarkholme]

thanks! I'm running the test again and hope it pass!

[HerringtonDarkholme]

I'm merging this anyway since the windows fix is not okay anyway. If possible, would you like to have a separate pr to fix the issue? thanks!

[StevenLove]

Thank you for your attention to detail in reviewing my code and for your helpful comments. I know you are busy so I've tried to avoid spamming you with notifications as best I know how.
I'm starting to accept that it may take some work to get the tests to pass on the windows CI, and I don't have a proper setup to do local windows development at the moment. I appreciate your decision to accept the PR and allow another PR to fix the test for windows.
There are some additional changes I would like to implement (the remaining TODOs) and perhaps I will gain some understanding of what is happening with windows as I make progress on those other changes.

I would appreciate any advice about how I can improve my contribution. Thank you.

[HerringtonDarkholme]

Hi @StevenLove, the failing windows test has been fixed by pinning dep versions.