Minor format tweak and off-by-one fix

[AThePeanut4]

Firstly, thank you for developing this plugin, and for all the work you've obviously put in to the rewrite. v3 is great ❤️

This PR just makes a minor tweak and fixes an off-by-one error.

The off-by-one is for the [row, col] display. ctx.item.pos seems to be (1, 0) indexed, so the +1 should be on the column, not the row.

The tweak is for the formatting of an item's "source". Currently there are three different ways this is displayed:

• Diagnostics have the source highlighted as a comment, before the position
• LSP definitions/references/etc have the client name highlighted as normal text, in brackets, before the position
• LSP incoming/outgoing calls have the client name highlighted as a "Title", without brackets, after the position

What I've done is change the LSP format strings to be more like the diagnostics one. This is what looks the nicest imo, but I don't really have a strong opinion here so if you feel differently then I don't mind changing it.

I've also changed the diagnostic formatting, so that the brackets around the code are also highlighted as a comment. Currently the brackets are shown as normal text, which looks a bit off to me, but again it's not a big deal and I wouldn't mind changing/reverting it.

These changes seem to work for me, but the code is quite complicated and I don't really understand much of what's going on - so it's very possible I've done something very wrong or missed something. Please feel free to fix/change anything if needed.

[folke]

I've just taken that pos fix from your PR and changed that already.
Still need to look into the format changes (later).
Thank you