Add mmdriley as review manager (#242)

As discussed at https://forums.carbon-lang.dev/t/looking-for-additional-review-managers

docs/project/evolution.md

@@ -103,6 +103,7 @@ team will still review participation.
 Our current review managers are:
 
 -   [jonmeow](https://github.com/jonmeow)
+-   [mmdriley](https://github.com/mmdriley)
 -   [sidney13](https://github.com/sidney13)
 
 ### Core team