Add michael@zed.dev to .mailmap (#20119)

Release Notes:

- N/A

.mailmap

@@ -60,6 +60,8 @@ Max Brunsfeld <maxbrunsfeld@gmail.com>
 Max Brunsfeld <maxbrunsfeld@gmail.com> <max@zed.dev>
 Max Linke <maxlinke88@gmail.com>
 Max Linke <maxlinke88@gmail.com> <kain88-de@users.noreply.github.com>
+Michael Sloan <michael@zed.dev>
+Michael Sloan <michael@zed.dev> <mgsloan@google.com>
 Mikayla Maki <mikayla@zed.dev>
 Mikayla Maki <mikayla@zed.dev> <mikayla.c.maki@gmail.com>
 Mikayla Maki <mikayla@zed.dev> <mikayla.c.maki@icloud.com>