Add docs for authenticating on reddit (#266)

Author: kadikraman

README.md

@@ -38,6 +38,7 @@ These providers implement the OAuth2 spec, but are not OpenID providers, which m
 * [Uber](https://developer.uber.com/docs/deliveries/guides/three-legged-oauth.md) ([Example configuration](./docs/config-examples/uber))
 * [Fitbit](https://dev.fitbit.com/build/reference/web-api/oauth2/) ([Example configuration](./docs/config-examples/fitbit.md))
 * [Dropbox](https://www.dropbox.com/developers/reference/oauth-guide) ([Example configuration](./docs/config-examples/dropbox.md))
+* [Reddit](https://github.com/reddit-archive/reddit/wiki/oauth2) ([Example configuration](./docs/config-examples/reddit.md))
 
 ## Why you may want to use this library
 

docs/config-examples/reddit.md

@@ -0,0 +1,30 @@
+# Reddit
+
+** This is Android Only **
+
+Log in and go to [apps](https://www.reddit.com/prefs/apps) to create your app.
+
+Choose "installed app" and give it a name, description and about url of your choosing.
+
+For the redirect uri, choose something like `com.myapp//oauth2redirect/reddit` and make sure that you use `com.myapp` in your `appAuthRedirectScheme` in `android/app/build.gradle`.
+
+Reddit requires for you to add a [basic auth header](https://github.com/reddit-archive/reddit/wiki/oauth2#retrieving-the-access-token) to the token request.
+
+```js
+const config = {
+  redirectUrl: 'com.myapp://oauth2redirect/reddit',
+  scopes: ['identity'], // include the scopes you need
+  serviceConfiguration: {
+    authorizationEndpoint: 'https://www.reddit.com/api/v1/authorize.compact',
+    tokenEndpoint: 'https://www.reddit.com/api/v1/access_token',
+  },
+  customHeaders: {
+    token: {
+      Authorization: 'Basic <base64encoded clientID:>',
+    },
+  },
+};
+
+// Log in to get an authentication token
+const authState = await authorize(config);
+```