[doc] Update release notes (#174)

Author: adangel

ReleaseNotes.md

@@ -25,10 +25,13 @@ This is a major release.
 * The PMD Designer can't be started from within the plugin anymore. Please install
   [PMD Designer](https://github.com/pmd/pmd-designer) separately when needed.
 
+* Updated to PMD 7.0.0-rc1
+
 ### Fixed Issues
 
 * [#122](https://github.com/pmd/pmd-eclipse-plugin/issues/122): Update PMD 7 Logo in eclipse pmd plugin
 * [#172](https://github.com/pmd/pmd-eclipse-plugin/issues/172): Only support the last 4 eclipse releases
+* [#174](https://github.com/pmd/pmd-eclipse-plugin/pull/174): Upgrade to PMD 7
 
 ### API Changes