everything(?) heroku needs for django-gulp

.buildpacks

@@ -0,0 +1,2 @@
+https://github.com/heroku/heroku-buildpack-nodejs.git
+https://github.com/heroku/heroku-buildpack-python.git

package.json

@@ -6,7 +6,6 @@
   "bugs": {
     "url": "https://github.com/mozilla/fx-private-relay/issues"
   },
-  "dependencies": {},
   "devDependencies": {
     "@mozilla-protocol/core": "^14.0.3",
     "del": "^6.0.0",

requirements.txt

@@ -4,6 +4,7 @@ dj-database-url==0.5.0
 django-allauth==0.39.1
 django-csp==3.5
 django-debug-toolbar==2.2.1
+django-gulp==4.1.0
 django-redis==4.12.1
 django-ftl==0.12.1
 django-referrer-policy==1.0