Docs updates for latest

[sgammon]

Feature description

We're missing a lot of docs, especially since Writerside shit the bed. Let's make a big list of what needs updating to get back up to parity and smooth CI/CD.

• Get Writerside working again for this last release
• Find a new docs framework
• Figure out how to port our current docs, or make a transition plan
• Add missing doc topics
  • Projects
  • Dependencies
  • Build graph
  • Test runner
    • Run *.test.* files
    • Run tests from test source set
    • Coverage flags
  • Regular runner entrypoint
  • elide help ...
  • Project scripts
  • Project entrypoints
  • New server API
  • Known missing features
  • Foreign manifests
  • kotlinc + javac + jar + javadoc
  • Kotlin built-ins
    • Dependencies
    • Kotlin compiler plugins