Choose whether note is resolvable

[jakubbortlik]

Feature Description

While working on #417, I've noticed that notes in gitlab.nvim are created as resolvable (i.e., as threads) when they are created directly with require("gitlab").create_note(), but as non-resolvable when they are first created as a draft note and then published. While I don't think this causes any real problems to users, it may be a little confusing why some notes need to be resolved and some not.

To match the behaviour of Gitlab online, (and if this is supported by go-gitlab) users should have the possibility of choosing whether they create a note as a non-resolvable comment or a thread. This could be implemented as another field in the note popup next to "Draft", something like "Type" with the values "Comment" and "Thread".

I've also just noticed, that Gitlab also allows creating "Internal notes". gitlab.nvim should probably at least show the internal flag on the note, ideally, also enable users to create internal notes (that could be another field in the note popup).

[jakubbortlik]

Regarding internal notes, there's a feature request in the new repo for the gitlab go client, so apparently this is not yet supported.