feat: auto select default providers based on installed plugins

[meronogbai]

Description

I wanted codecompanion to respect .gitignore when selecting files via the /file slash command. I initially thought this was a missing feature, but I managed to get it working by using telescope as the provider. Most likely because I had configured Telescope to respect ignore files globally.

This was surprising because I assumed codecompanion already used telescope by default. So I figured, why not make that behavior official?

Related Issue(s)

#1185

Checklist

• I've read the contributing guidelines and have adhered to them in this PR
• I've updated the README and/or relevant docs pages
• I've run make docs to update the vimdoc pages

[meronogbai]

Running make docs adds unrelated changes and I couldn't update docs because I don't know which files I should update. 👀

[olimorris]

Can we keep this as config.lua please. Don't understand why you've renamed it to config/init.lua. This is a great PR but doesn't need a structure change.

[olimorris]

We also need to document this for other users, in the configuration section of the docs

[meronogbai]

@olimorris Done! LMK what you think 🫡

[olimorris]

So this is very, very awesome and will clean up people's config tremendously. Thanks for your efforts! Worked out of the box brilliantly for me and will be a huge improvement on the default experience for a lot of people.

I've added in some minor comments.

[meronogbai]

TY @olimorris. For some reason, I can't see the comments. Did you forget to click the submit review button?

[olimorris]

Me right now

[meronogbai]

No worries!

[olimorris]

Once again, thank you! Amazing feature and a huge benefit to so many users