Add Transifex project url for contributors to find easier (#32)

* Add Transifex project url for contributors to find easier

In order to help contributors to find the user documentations translation project easier, this commit adds a new paragraph that points to that project.

* Remove tfx link and minimize translation hints

As on Ryans suggestion the translation block has been corrected to a smaller and easier version.
This also removes the direct "transifex.com" link which might confuse.

As on comment #32 (review)

README.md

@@ -12,10 +12,9 @@ If you would like to improve the docs, simply:
 2. edit the appropriate `.rst` files (see [Markup Format](#markup-format) below), and
 3. submit a pull request.
 
-> **🌍 Note on localization:** Translations are prepared and stored on
-> [Transifex][tfx], a third-party cloud platform. Do **NOT** manually edit the
-> `.po` and `.mo` localization files, as any such changes will be overwritten
-> in the compilation process.
+> 🌍 **Wanna help translate?** Submit your contributions
+> (or request additional languages) [here][tfxtranslate].
+> Do **NOT** submit a PR with changes to the contents of the `locale/` directory.
 
 Thanks! ❤ ❤ ❤  
 The Zammad Team
@@ -95,4 +94,4 @@ $ make -e SPHINXOPTS="-D language='en'" html
 
 [badge]: https://readthedocs.org/projects/zammad-user-documentation/badge/?version=latest
 [docs]: https://zammad-user-documentation.readthedocs.io/en/latest/
-[tfx]: https://www.transifex.com/
+[tfxtranslate]: https://www.transifex.com/zammad/zammad-user-documentation/