Add a mailmap for better "git shortlog -nse"

ctrueden · ctrueden · commit 9223b8e96667 · 2022-08-26T11:05:04.000-05:00
diff --git a/.mailmap b/.mailmap
@@ -0,0 +1 @@
+Jan Eglinger <jan.eglinger@fmi.ch> <jan.eglinger@gmail.com>

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+Jan Eglinger <jan.eglinger@fmi.ch> <jan.eglinger@gmail.com>`