Add scripts/validate-config.sh

Run this from a pre-push hook to validate the configuration files before
pushing changes to github. Note that this does not validate vault .hcl
policy files; it simply verifies the syntax of any jsonnet, json, or YAML
files in the config directory.

scripts/validate-config.sh

@@ -0,0 +1,17 @@
+#!/bin/sh
+
+fakedata=$(mktemp -d fakedataXXXXXX)
+trap 'rm -rf $fakedata' EXIT
+
+set -eu
+
+# This is a bit of hack to locate all the paths required by "importstr"
+# statements and then create corresponding empty files in the
+# fakedata directory.
+find config -type f -print0 |
+	xargs -0 grep importstr |
+	grep -E 'tokens|secrets' |
+	cut -f2 -d'"' |
+	xargs -IPATH sh -c 'mkdir -p "$1/${2%/*}"; touch "$1/$2"' -- "$fakedata" PATH
+
+python apply_vault_config.py -l -d "$fakedata" > /dev/null