Improve UX on configuring suggestions behavior

[ildella]

please complete the following information:

• OS version: [Ubuntu 20.04]
• Editor version: Sublime 4 - build 4124
• Programming language: [js]
• Tabnine extension version: 4.0.29-41

Issue Details:

When I first installed Tabnine, I started getting suggestions as expected, but along with lots of other suggestions from Sublime default suggestion engine.

As Tabnine's are better, I wanted to mostly exclude Sublime ones.

I did almost succeed eventually setting this in Preferences.sublime-settings

"auto_complete_use_index": false

The result is I get all Tabnine and almost zero other suggestions, which is fine.
Also good I still get "snippets" from other exetnsions when needed.

Still this is not great UX or onboarding.
It would be great to dig into the problem and find out a solution that explain to the user the various options of using tabnine in combination with default Sublime 4 suggestions. For instance it would be great to have a way to sort suggestions: Tabnine first, Sublime later.

gz#9903