1010: Move the localization effort to Weblate r=mergify[bot] a=kaiyou
## What type of PR?
documentation
## What does this PR do?
This PR updates documentation for us to move the localization effort outside of POEditor. POEditor had archived our project and it was linked to my account. I suggest we move to a Weblate instance (hosted at TeDomum for the part I setup).
### Related issue(s)
- closes#916
## Prerequistes
Before we can consider review and merge, please make sure the following list is done and checked.
If an entry in not applicable, you can check it or remove it from the list.
- [x] In case of feature or enhancement: documentation updated accordingly
- [x] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/guide.html#changelog) entry file.
Co-authored-by: kaiyou <pierre@jaury.eu>
- Enable bors-ng for better merging
- Re-enable mergify with a fixed up syntax, it will now only issue bors commands.
- Pull request build images are now pushed to docker hub
- Automatic backport rule
- Fix build tag for branches with slash (/)
- Only push when master and 1.6 target branch
