Add missing documentation

[moritzfl]

Adds missing markdown files for various vale configuration options to the docs folder.

This currently only modifies/adds markdown files, it does not include any modifications to code

I am not using vale-ls and am not familiar enough with rust or the codebase to the extent that I felt confident enough to also test and integrate it in code. I am however willing to take a stab at it if you want me to.

This PR is a result of my work on a PR to the vale-cli plugin for IntelliJ over here: https://gitlab.com/pablomxnl/vale-cli-plugin/-/merge_requests/62

[moritzfl]

This is somewhat linked to this Pull Request but it is an idea I had during implementation. So I thought I might as well suggest it here.

What do you think about switching the documentation format for code highlighting in yml files to a json schema? (https://json-schema.org/specification)

LSP support is pretty neat but while vale evolves and thrives, it seems like vale-ls is less of a focus. Having ready to use schemas that work directly in IDEs could make it easier to support vale in the best way possible in IDE integrations - even when not relying on vale-ls.

Some IDEs integrate support for json schemas directly and thus documentation on hover, validation and autocomplete is already implemented directly without much work from the vale project. (there is a quick description/summary on https://www.schemastore.org for this)

And if vale supported yml configurations as well instead of or in addition to the .vale.ini format, we could also cover that.

There is also a pretty well maintained library for go and json schema:

• https://github.com/google/jsonschema-go

Perhaps the schema can be generated directly from vale's code which would automatically keep it in sync with the implementation.