Fix Heroku deploy button

Gemfile

@@ -63,3 +63,5 @@ gem 'refinerycms-wymeditor', git: 'https://github.com/parndt/refinerycms-wymedit
 
 # The default authentication adapter
 gem 'refinerycms-authentication-devise', git: 'https://github.com/refinery/refinerycms-authentication-devise', branch: 'master'
+
+gem 'mimemagic', github: 'mimemagicrb/mimemagic', ref: '01f92d86d15d85cfd0f20dabd025dcbd36a8a60f'

Gemfile.lock

@@ -1,3 +1,10 @@
+GIT
+  remote: https://github.com/mimemagicrb/mimemagic.git
+  revision: 01f92d86d15d85cfd0f20dabd025dcbd36a8a60f
+  ref: 01f92d86d15d85cfd0f20dabd025dcbd36a8a60f
+  specs:
+    mimemagic (0.3.5)
+
 GIT
   remote: https://github.com/parndt/refinerycms-wymeditor
   revision: 18571cd34ef30f7fba397c0623248eb25191abb7
@@ -206,7 +213,6 @@ GEM
     marcel (0.3.3)
       mimemagic (~> 0.3.2)
     method_source (0.9.2)
-    mimemagic (0.3.3)
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
     minitest (5.13.0)
@@ -352,6 +358,7 @@ DEPENDENCIES
   capybara (>= 2.15)
   jbuilder (~> 2.7)
   listen (>= 3.0.5, < 3.2)
+  mimemagic!
   pg (>= 0.18, < 2.0)
   puma (~> 4.3)
   rails (~> 6.0.2)

README.md

@@ -1,3 +1,12 @@
 # Refinery Example App
 
+## Deploy to Heroku
+
   [![Deploy](https://www.herokucdn.com/deploy/button.svg)](https://heroku.com/deploy?template=https://github.com/refinery/refinery-example-app)
+
+## Installation on localhost
+
+If you start the project on localhost, the `error Couldn't find an integrity file` will be raised. Fix it by `yarn install --check-files`
+
+If the another error `[email protected]: The engine "node" is incompatible with this module. Expected version "12.13.0". Got "XX.YY.ZZ"` is raised, it is because you dont have exact version
+of node - v12.13.0 installed. Ignore this error by running command `yarn install --ignore-engines` 

app.json

@@ -11,6 +11,14 @@
       "cms",
       "ruby"
     ],
+    "buildpacks": [
+      {
+        "url": "heroku/nodejs"
+      },
+      {
+        "url": "heroku/ruby"
+      }
+    ],
     "addons": [
       "heroku-postgresql:hobby-dev"
     ],
@@ -31,5 +39,6 @@
       "SECRET_KEY_BASE": {
         "generator": "secret"
       }
-    }
+    },
+    "stack": "heroku-18"
   }

package.json

@@ -8,6 +8,9 @@
     "@rails/webpacker": "4.2.2",
     "turbolinks": "^5.2.0"
   },
+  "engines": {
+    "node": "12.13.0"
+  },
   "version": "0.1.0",
   "devDependencies": {
     "webpack-dev-server": "^3.9.0"