Port docs about "Glowstone Documentation" from the wiki

### Task
Port the pages from the [Glowstone Documentation](https://github.com/GlowstoneMC/Glowstone/wiki#glowstone-documentation) in the Glowstone wiki.

### Details
These should be individual pages under the [`Design Documents`](https://docs.glowstone.net/en/latest/Development/Design_Documents/index.html) page/section.

### Guide
[Contributing to Docs](https://docs.glowstone.net/en/latest/Development/docs.html)

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