Prepare new Greeter documentation for inline help

In several places in the new Greeter we have help buttons pointing people to the documentation. This documentation should be prepare to received each of these help buttons.

Ideally, each info button would point to a dedicated page with only the relevant information. But if we also want to have this information in the general documentation, then we need to rely on inline which are sometimes problematic. In this particular case, inlines might not be worth it and we’ll instead point people to sections of the general documentation about Tails Greeter:

• Point the info button on “Language & Region” to a new section of /doc/first_steps/startup_options right below the Greeter screenshot.
• Remove the info button on “Encrypted Persistent Storage” because only people who already have a persistent storage would see that. It will be much more relevant once people will be able to create the persistent storage from the Greeter (#12379).
• Point the info button on “Additional settings” to a new section of /doc/first_steps/startup_options improving on the current index of dedicated pages per settion.
• Add a “More info” link below the paragraph describing each additional setting and pointing to :
  • /doc/first_steps/startup_options/administration_password
  • /doc/first_steps/startup_options/mac_spoofing
  • /doc/first_steps/startup_options/network_configuration
• Hide the side bar on embeded documentation.

Feature Branch: doc/5680-new-greeter

Parent Task: #5680 (closed)

Related issues

• Blocks #12432 (closed)

Original created by @sajolida on 11949 (Redmine)