Add .mailmap file

There are a few commits in Bedstead's history that have incorrect email
addresses for me.  This corrects them.

diff --git a/.mailmap b/.mailmap
new file mode 100644 (file)
index 0000000..b37ae0a
--- /dev/null
+++ b/.mailmap
@@ -0,0 +1,2 @@
+Ben Harris <bjh21@bjh21.me.uk> <bjh21@cam.ac.uk>
+Ben Harris <bjh21@bjh21.me.uk> <bjharris@chiark>