Most of the definitions are based on the documentation in
`internal/manager/config/config.go` or inferred by labels and
descriptions from Flamenco v2 config pages.
Reviewed-on: https://projects.blender.org/studio/flamenco/pulls/104400
A few minor adjustments:
- Added a note about the job type being third-party, and what that implies.
- Removed the need to use Git or the mention of symlinks, to simplify
installation instructions.
- Fixed a few markup issues.
Additions to the documentation:
- Page for collecting custom job types, with multi-pass job type.
- BAT Pack Error Message solution on Windows.
- Clarificationof two-way variable usage in jobs.
Reviewed-on: https://projects.blender.org/studio/flamenco/pulls/104202
