Enable Markdown checks on Weblate

Originally created by @sajolida on #17358 (Redmine)

According to one of our sysadmins, Weblate was updated to 3.5 but without the Markdown checks.

Having Markdown checks was deemed as a requirement before doing tails#16221 (closed), see tails#16221 (comment 15652), which would simplify quite a bit the work of technical writers and translators.

Feature Branch: https://salsa.debian.org/hefee/puppet-tails:hefee/17358-markdown-checks-on-weblate

Related issues

Blocked by #16943 (closed)
Blocks tails#16221 (closed)

Edited May 15, 2020 by sajolida

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information