add translation badge to README

[felixhaeberle]

Hey there, we want to get you more contributors to your repository! Therefore, I added a badge which lets users contribute to your translations.

The badge endpoint allows you to create a dynamic badge that display real-time data on your project. For instance, you can use it to showcase your project's localization progress or the number of errors/warnings on your Github repository. This means that whenever someone views the badge, they will see the most up-to-date information about your project.

For your project, the badge looks like this: (this image is already auto generated)

We would be really happy if you decide to place this into your README to let people contribute to your translations 🥰

– Thank you, Felix