add 'Extract Burnin' docs

[MustafaJafar]

Changelog Description

Add Extract Burnin documentation.
Here's a sneak peek from the update.

[ynbot]

Task linked: AY-5526 Burnins and how to guide

[jakubjezek001]

I think it would be helpful to include a link to the available anatomy tokens. It's worth noting that some tokens are only for certain hosts; we should mention this too. Plus, I think we can connect specific burn-in presets from the extract review presets. We should highlight that as well.

[MustafaJafar]

It's worth noting that some tokens are only for certain hosts

Is there a way other than trial and error to check if a token is not supported on a particular host?
I also noticed that some tokens already used in settings are not showing up in Available template keys
e.g.

• {anatomy[version]}
• {username}
• {folder[name]}
• {frame_start}
• {current_frame}
• {frame_end}

[MustafaJafar]

Hey, I've added the notes in my last two commits.

[jakubjezek001]

Brilliant, thanks!