[Task]: add Weblate to translation contribution guide

[bamaer]

What needs to happen?

the translation contribution guide doesn't mention Weblate yet.

suggested approach: add Weblate as the preferred option for now. Move Hop Translator down the page as the old-school translation tool, and gradually phase it out.

Issue Priority

Priority: 3

Issue Component

Component: Documentation

[nadment]

To be specified in the translation guide:

Whenever writing single quote, it should be written as '' two single quotes (U+0027 U+0027). When not paired, it is treated as beginning of quoting and will not be shown when rendering the string.

https://docs.weblate.org/en/latest/user/checks.html#java-messageformat

[hansva]

.take-issue

[hansva]

Follow up ticket to remove the translator from our codebase #4035