Shake CI and docs up

ci/clean.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+main() {
+  git clean -xffd
+  git submodule foreach --recursive git clean -xffd
+  git submodule foreach --recursive git reset --hard
+}
+
+main "$@"