Host the Debian Live Manual for live-build 2.x

Originally created by @anonym on #12296 (Redmine)

I.e. host on our infra a version of the manual that is valid for our live-build “fork” (unlike the official one which is for a much more recent version than ours, and tons of stuff differs, rendering it useless for Tails). The manual would be really useful for new contributors.

Related issues

• Related to tails#5691 (closed)
• Blocks tails#12261 (closed)