Update AUTHORS and .mailmap

The AUTHORS file was updated with the following command, moving duplicate
entities to the .mailmap first.

> git log --use-mailmap --format='format:%aN <%aE>' \
>   | grep -v '^dependabot' \
>   | sort -u > AUTHORS

.mailmap

@@ -1,7 +1,9 @@
 Alexander A. Klimov <[email protected]> <[email protected]>
+Alvar Penning <[email protected]> <[email protected]>
 Diana Flach <[email protected]> <[email protected]>
 Diana Flach <[email protected]> <[email protected]>
 Diana Flach <[email protected]> <[email protected]>
+Eric Lippmann <[email protected]> <[email protected]>
 Henrik Triem <[email protected]> <[email protected]>
 Julian Brost <[email protected]> <[email protected]>
 <[email protected]> <[email protected]>

AUTHORS

@@ -1,11 +1,18 @@
 Alexander A. Klimov <[email protected]>
 Alvar Penning <[email protected]>
+Blerim Sheqa <[email protected]>
+Diana Flach <[email protected]>
 Eric Lippmann <[email protected]>
 Feu Mourek <[email protected]>
 Henrik Triem <[email protected]>
 Johannes Meyer <[email protected]>
+Jonada Hoxha <[email protected]>
 Julian Brost <[email protected]>
+Justin Müller <[email protected]>
+Markus Frosch <[email protected]>
 Michael Friedrich <[email protected]>
+Michael Insel <[email protected]>
+mzac <[email protected]>
 Noah Hilverling <[email protected]>
 Ravi Kumar Kempapura Srinivasa <[email protected]>
 Yonas Habteab <[email protected]>