Add settings and added extra styles for single/trailing spaces

[jjspace]

• Create a settings page to enable configuration on a per character basis
  • The settings for single characters and all spaces are linked because you should only care to modify the single space setting if you're showing spaces in the first place. There is extra logic to account for this.
  • The setting for trailing spaces is kept "unlinked" as it is common to want to show trailing spaces but not other spaces (see #6)
• Added styling for single characters (those in between words) and trailing characters (those at the end of lines)

This will enable people to have different configurations as well as brings it closer in line with how showing whitespace works in code editors like vscode

I referenced the sample plugin for how to create settings like so

Resolves #6

[jjspace]

@deathau I'm not sure how you're versioning or how publishing to Obsidian works so please either let me know or make sure to make those changes before merging this branch!

[deathau]

@deathau I'm not sure how you're versioning or how publishing to Obsidian works so please either let me know or make sure to make those changes before merging this branch!

The way this (generally) works, is I'll commit a bunch of stuff (or in this case merge PRs) and then when I'm happy with it I'll create a release and bump the version number in the manifest. My point being: I'm merging your PR, and after I tidy up some other stuff, I'll create a release with all this stuff.

By the way, thanks for all this. Saves me the work. I really appreciate it.