Add AUTHORS file and script

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

scripts/generate-authors.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+set -e
+
+cd "$(dirname "$(readlink -f "$BASH_SOURCE")")/.."
+
+# see also ".mailmap" for how email addresses and names are deduplicated
+
+{
+	cat <<-'EOH'
+	# This file lists all individuals having contributed content to the repository.
+	# For how it is generated, see `scripts/generate-authors.sh`.
+	EOH
+	echo
+	git log --format='%aN <%aE>' | LC_ALL=C.UTF-8 sort -uf
+} > AUTHORS