Chore: Restructure docs

[Hugos68]

Changes:

1. All collections are now categories under the docs collection.
2. All categories are accompanied with a meta.mdx with metadata related to that category.
3. Added src/content/config.ts with zod schema's to create type safe frontmatter.
4. Added src/content/docs.ts with helpers to retrieve stuff like metadata from a category, all the categories, etc