update readme development server link (#764)

README.md

@@ -30,7 +30,7 @@ For developers:
 
 - Improved [bare metal/VM guide](https://docs.joinmbin.org/admin/installation/bare_metal) and [Docker guide](https://docs.joinmbin.org/admin/installation/docker/)
 - [Improved Docker setup](https://github.com/MbinOrg/mbin/pulls?q=is%3Apr+is%3Amerged+label%3Adocker)
-- _Developer_ server explained (see "Developers" section down below)
+- _Developer_ server explained (see [Development Server documentation here](https://docs.joinmbin.org/contributing/development_server) )
 - GitHub Security advisories, vulnerability reporting, [Dependabot](https://github.com/features/security) and [Advanced code scanning](https://docs.github.com/en/code-security/code-scanning/introduction-to-code-scanning/about-code-scanning) enabled. And we run [`local-php-security-checker`](https://github.com/fabpot/local-php-security-checker).
 - Improved **code documentation**
 - **Tight integration** with [Mbin Weblate project](https://hosted.weblate.org/engage/mbin/) for translations (Two way sync)