Use Gitlocalize instead of Weblate

[fflorent]

After having played with Weblate, it appeared that it is hard to be used, especially when translating the markdown.

Gitlocalize, despite not being Free Software, would be a better fit, the UI is much more intuitive, and would probably fit all of our needs.

TODO:

• [ ] Translate 2/3 pages using this solution
• [ ] Create a PR
• [ ] Submit feedback here