Mention New Feature in release notes

The command-line options of `git-bash.exe` [are now
documented](git-for-windows/MINGW-packages#36)
(call `git help git-bash`).

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

ReleaseNotes.md

@@ -39,6 +39,7 @@ This package contains software from a number of other projects including Bash, z
 
 * Comes with [tig v2.5.0](https://github.com/jonas/tig/releases/tag/tig-2.5.0).
 * Comes with [patch level 4](https://github.com/git-for-windows/msys2-runtime/commit/1bfdf956dae03d59bfe44b1e5882403ab803a67b) of the MSYS2 runtime (Git for Windows flavor) based on [Cygwin 3.0.7](https://cygwin.com/ml/cygwin-announce/2019-04/msg00030.html).
+* The command-line options of `git-bash.exe` [are now documented](https://github.com/git-for-windows/MINGW-packages/pull/36) (call `git help git-bash`).
 
 ### Bug Fixes