Disable/Enable tabby by filetype

[bogzbonny]

This is a standard feature that most other code completion providers offer. Personally I find code completion distracting when I'm editing non-code (eg. markdown). The two main implementation Options I can think of is:

• disable all, then have a manually enabled filetype list
• enable all (default), then have a manually disabled filetype list

I've also seen other setups (eg. supermaven) where there is an option for a script input which runs to determine if the file should have code-completion or not, but this seems like overkill imo