[ISSUE-296] Add support for fish autocompletions

[KristianLentino99]

Hi all, I wanted to contribute a little bit to this fantastic project so I've taken a look at your "Good first Issues" and I've decided to pick up this one.

• I've updated the related test and ran all the steps mentioned in the CONTRIBUTING guidelines.
• I've also updated the Advanced installation doc adding the tab for the new fish CLI.

I've also ran scala-cli with my changes locally and installed it from scratch to test if it works:

[tgodzik]

Thanks! I tested it out and look to work except when using completion without any input. That seems to be case app issue though and can be further improved.

[tgodzik]

Actually works fine, I had leftover code from a previous attempt. I wonder if we could get also next subcommands, it doesn't seem implemented in case app (or scala-cli?)

[tgodzik]

Ad 3. Looks like some subcommands work, while other do not (bloop about is not suggested). Anyway looks like we can improve things further, but this already works awesome!

[Gedochao]

Ad 3. Looks like some subcommands work, while other do not (bloop about is not suggested). Anyway looks like we can improve things further, but this already works awesome!

@tgodzik Can you extract any issues you've found into separate issues?

[Gedochao]

Looks good, thanks for the contribution!

[tgodzik]

Ad 3. Looks like some subcommands work, while other do not (bloop about is not suggested). Anyway looks like we can improve things further, but this already works awesome!

@tgodzik Can you extract any issues you've found into separate issues?

Funny thing, those commands do not exist in Scala CLI codebase, but they work since they are just forwarded to Bloop, which understands more commands. The question is whether they should be showed by Scala CLI?

This is things like scala bloop projects or even scala bloop compile both of which will actually not work unless run in scala-build directory 😅

The only one I think we could add is about