Add deploying-to-heroku.md

docs/docs/deploying-to-heroku.md

@@ -0,0 +1,48 @@
+---
+title: Deploying to Heroku
+---
+You can use the [heroku buildpack static](https://github.com/heroku/heroku-buildpack-static) to handle the static files of your site.
+
+Set the `heroku/node.js` and `heroku-buildpack-static` buildpacks on your application creating an `app.json` file on the root of your project.
+
+app.json:
+```
+{
+  "buildpacks": [
+    {
+      "url": "heroku/nodejs"
+    },
+    {
+      "url": "https://github.com/heroku/heroku-buildpack-static"
+    }
+  ]
+}
+```
+
+Sometimes specifying buildpacks via the `app.json` file doesn’t work. If this is your case try to add them in the Heroku dashboard or via the CLI.
+
+Add a `heroku-postbuild` script in your `package.json`:
+
+package.json:
+```
+{
+  // ...
+  "scripts": {
+    // ...
+    "heroku-postbuild": "gatsby build"
+    // ...
+  }
+  // ...
+}
+```
+Finally, add a `static.json` file in the root of your project to define the directory where your static assets will be. You can check all the options for this file in the [heroku-buildpack-static](https://github.com/heroku/heroku-buildpack-static#configuration) configuration.
+```
+{
+  "root": "public/",
+  "headers": {
+    "/**.js": {
+      "Cache-Control": "public, max-age=0, must-revalidate"
+    }
+  }
+}
+```