Improve folder/file selection text input UX

[zachmueller]

Improve this to include helper functionality like other plugins have that pop up with folders/files as the user types in the input box to help auto-complete following the correct syntax. Places in settings thus far include: Capture thought -> Note directory, Spacing methods -> Custom script. Possibly related code for reference, from Periodic Notes: file-suggest.ts and NoteTemplateSetting.svelte.