Provide default fileNesting patterns

[MangelMaxime]

Fix #1724

Adding the configuration like done in this PR seems to be enough to have nesting pattern added for F#.

This configuration is merged with the default configuration from VSCode:

The picture above is the result of doing Fable.Core.JS.console.log (Configuration.getUnsafe "explorer.fileNesting.patterns") when loading Ionide.

However, the drawback I see is that if the user don't want the nested feature for F# files and he try to set its configuration then the default value completed doesn't contain the default configuration from VSCode but only the ones from Ionide.

Screen.Recording.2023-03-11.at.22.31.54.mov

Personally, I think this is problem in VSCode and not in Ionide.

If we want, to preserve the defaults configuration then, we would need to do something similar to Suggest gitignore:

• Ask the user if he wants F# nesting patterns.
• If yes
  • Retrieve the current nesting patterns settings
  • Merge with F# nesting patterns and save in the workspace settings
• If no, discard or save user choice to not suggest again

[baronfel]

Thanks for doing this :)

[MangelMaxime]

Always happy to help :)

Doing a tour of the issues I can fix in Ionide.