Feat: add Transifex link to README (#1317)

## Checklist before requesting a review

*Please delete options that are not relevant.*

- [x] I have performed a self-review of my code.
- [ ] I have added tests (when available) that prove my fix is effective
or that my feature works.
- [x] I have updated the CHANGELOG with a short functional description
of the fix or new feature.
- [ ] This change requires a documentation update.

## Description

- It fixes #N/A
- Translators can now find the Transifex project from the README, so
that missing languages can be contributed there and synchronized back
into the plugin.

## Screenshots (if appropriate):

Author: Rom1-B

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+### Added
+
+- Add Transifex translations link to README
+
 ### Fixed
 
 - Fix mandatory fields of a block hidden by its display conditions blocking the save of an item

README.md

@@ -294,3 +294,7 @@ Obtain a personalized service experience, associated with benefits and opportuni
 ## Copying
 
 * **Code**: you can redistribute it and/or modify it under the terms of the GNU General Public License ([GPL-2.0](https://www.gnu.org/licenses/gpl-2.0.en.html)).
+
+## Additional resources
+
+* [Translations on Transifex](https://explore.transifex.com/teclib/glpi-plugin-plugin-fields/)