database: Add mailmap

This gets used by git shortlog to map people who
have used different identities across their contributions
to this repository into a single shortlog entry.

Signed-off-by: Harsh Shandilya <harsh@prjkt.io>

.mailmap

@@ -0,0 +1,7 @@
+Harsh Shandilya       <harsh@prjkt.io>
+Harsh Shandilya       <msfjarvis@gmail.com>
+Nathan Chancellor     <natechancellor@gmail.com>
+Nathan Chancellor     <nathan@prjkt.io>
+Nathan Chancellor     <nathanchance@users.noreply.github.com>
+Piere R               <piereralph@gmail.com>
+Piere R               <pierx@users.noreply.github.com>