add package.json for conveniently installing tools

process_static

@@ -2,6 +2,8 @@
 
 set -o errexit -o nounset -o pipefail
 
+export PATH="$PWD/node_modules/.bin:$PATH"
+
 rm -rf static_tmp
 cp -a static static_tmp
 json_reformat -m < static_tmp/manifest.webmanifest | sponge static_tmp/manifest.webmanifest