Tidy up the top-level directory by moving misc. scripts into a subdirectory.

scripts/format-all.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+set -euo pipefail
+
+# Format all sources using rustfmt.
+
+topdir=$(dirname "$0")
+cd "$topdir"
+
+# Make sure we can find rustfmt.
+export PATH="$PATH:$HOME/.cargo/bin"
+
+exec cargo +stable fmt --all -- "$@"