Provide a better link for onboarding of volunteers from "Get Involved…

…" link in readme

Provide a better link for onboarding of volunteers from "Get Involved" link in readme

Used to be just joomla.org homepage - proposing a link to http://volunteers.joomla.org/ instead

README.md

@@ -79,7 +79,7 @@ Do you want to improve Joomla?
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 * How do you [request a feature](https://docs.joomla.org/How_do_you_request_a_feature%3F)?
 * How do you [report a bug](https://docs.joomla.org/Filing_bugs_and_issues)?
-* Get Involved: Joomla! is community developed software. [Join the community](http://www.joomla.org).
+* Get Involved: Joomla! is community developed software. [Join the community](http://volunteers.joomla.org/).
 * Documentation for [Developers](https://docs.joomla.org/Developers).
 * Documentation for [Web designers](https://docs.joomla.org/Web_designers).