Improve the CSS of our tables

Originally created by @sajolida on #15688 (Redmine)

We’re using table in our documentation in very important places to display complex information.

Their style is pretty poor, they are unappealing and hard to read:

• https://tails.boum.org/install/inc/steps/not_at_all.inline/
• https://tails.boum.org/doc/first_steps/accessibility/#index2h1
• https://tails.boum.org/doc/first_steps/startup_options/
• https://tails.boum.org/support/known_issues/graphics/#index1h2
• https://tails.boum.org/doc/encryption_and_privacy/veracrypt/#index1h2 (not merged yet)

Let’s make them fancier and easier to read!

/!\ ikiwiki uses table to display images with caption. See /news/version_2.0.mdwn for example.

Feature Branch: web/15688-better-tables

Related issues

• Blocks #15392 (closed)