Add readme

README.md

+# Google OpenID Connect / Oauth2.0 support
+Adds Google (Google Identity Platform » OpenID Connect) as an identity provider for user authentication and registration.
+
+## Pre-configuration
+Google requires that you create a client key specific to your installation to authenticate with the Google API. 
+To do this, follow the instructions under "*Obtain Oauth 2.0 credentials from the Google API console*", here: <https://developers.google.com/identity/protocols/OAuth2>
+
+When prompted, use the values listed below:
+
+**Name**<br>
+*<e.g. My Company The Bug Genie installation>*<br>
+**Authorized Javascript origins**<br>
+*Leave blank*<br>
+**Authorized redirect URIs**<br>
+\<http[s]://your.thebuggenie.com\>/oauth2_google/login 
+
+## Installation
+Either install from the modules section in The Bug Genie configuration, or download and install from
+[thebuggenie.com » Addons » Google authentication](http://thebuggenie.com/addons/oauth2_google)