feat (commands): add "create unique note" command

[alphashuro]

Adds an lsp command similar to obsidian's "unique note" builtin feature, which creates a new note file with a unique name based on a "unique note format" setting configured similar to the "daily note" setting. This change also skips "unique" file names that already exist by appending an incremental number to the note name to avoid conflicts, just as obsidian does.

It also includes a link_filenames_only setting which, after realising that the unique notes were inserted as date#heading, I realised was necessary

[alphashuro]

actually I just remembered I already merged the link filenames only feature 🤔 I wonder why it's been added again to the diff, will check