Add CI format check script

bin/html-beautify-check.sh

@@ -0,0 +1,22 @@
+# A custom script, that formats the file(s) with html-beautify,
+# but instead of changing it, it only errors with 0/1 if it needs to be changed
+# Ref: https://web.archive.org/web/20190522172323/https://medium.com/@jtomaszewski/keep-your-code-clean-forever-65c71f7f2df
+APPDIR=$(realpath $(dirname $(dirname $0)))
+TMPDIR=$(mktemp -d)
+cd $APPDIR
+
+for line in $*; do
+  filepath=$(realpath $line)
+  file=${filepath/$APPDIR\//}
+  mkdir -p $TMPDIR/$(dirname $file)
+  cp $APPDIR/$file $TMPDIR/$file
+done
+
+message=$(find $TMPDIR -type f | xargs node_modules/.bin/html-beautify -r | grep -v unchanged || true)
+if [[ $message ]]; then
+  echo "$message" | sed "s#$TMPDIR##g" | sed "s#\.\.\/##g"
+  rm -rf $TMPDIR
+  exit 1
+fi
+
+rm -rf $TMPDIR