Mention New Feature in release notes

`git version --build-options` now [also reports the
architecture](git-for-windows/git#866).

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 [Git v2.10.0](https://github.com/git/git/blob/v2.10.0/Documentation/RelNotes/2.10.0.txt).
 * The `git rebase -i` command was made faster by reimplementing large parts in C.
 * After helping the end-users to use the new defaults for PATH and FSCache, the installer [now respects the saved settings again](https://github.com/git-for-windows/build-extra/compare/a0a8613c54c0bd651904432f07f7b2999790b097~2...a0a8613c54c0bd651904432f07f7b2999790b097).
+* `git version --build-options` now [also reports the architecture](https://github.com/git-for-windows/git/pull/866).
 
 ### Bug Fixes