Creates the Github Source Documentation (#159)

Author: JeffNeff

docs/images/github/personal_access_token.png

@@ -0,0 +1,49 @@
+# Event Source for Github
+
+This event source creates a webhook to listen for incoming Github Events, turning received requests into [CloudEvents][ce] to be consumed by other TriggerMesh components.
+
+## Prerequisite(s)
+
+- GitHub Tokens
+
+### Create GitHub Tokens
+Create a personal access token for GitHub that the GitHub source can use to register webhooks with the GitHub API. Also decide on a secret token that your code will use to authenticate the incoming webhooks from GitHub (secretToken).
+
+The token can be named anything you find convenient. The Source requires `repo:public_repo` and `admin:repo_hook`, to let it fire events from your public repositories and to create webhooks for those repositories. Copy and save this token; GitHub will force you to generate it again if misplaced.
+
+Here's an example for a token named "GitHubSource Sample" with the recommended scopes:
+
+![ght](../images/github/personal_access_token.png)
+
+## Deploying an Instance of the Source
+
+Open the Bridge creation screen and add a source of type `Github`.
+
+In the Source creation form, give a name to the event source and add the following information:
+
+- **Secret**: Reference to a [TriggerMesh secret][tm-secret] containing an Access Token and Secret Token, as described in the previous sections.
+- **Name**: all TriggerMesh components need a unique name per namespace.
+- **Broker**: request converted into [CloudEvents][ce] will be sent to this location.
+- **Repository owner and Name**: A valid GitHub public repository owned by your GitHub user. (eg. <YOUR USER>/<YOUR REPO>).
+- **Event Types**: Select from the dropdown the types of events the source should emit. 
+
+After clicking the `Save` button, you will be taken back to the Bridge editor. Proceed by adding the remaining components to the Bridge, then submit it.
+
+A ready status on the main _Bridges_ page indicates that the event source is ready to receive notifications from the Github Event Source.
+
+![Bridge status](../images/bridge-status-green.png)
+### Verify
+
+Verify the GitHub webhook was created by looking at the list of webhooks under the Settings tab in your GitHub repository. A hook should be listed that points to your Knative cluster with a green check mark to the left of the hook URL, as shown below.
+
+![wh](../images/github/webhook_created.png)
+
+### More Information 
+More information on the Github Event Source can be found here: https://knative.dev/docs/eventing/samples/github-source/
+
+## Event Types
+
+The Github event source emits events that begin with `dev.knative.source.github.` and end in the event type. For example: `dev.knative.source.github.pull_request`, `dev.knative.source.github.create`, and `dev.knative.source.github.delete`.
+
+[tm-secret]: ../guides/secrets.md
+[ce]: https://cloudevents.io

docs/images/github/webhook_created.png

@@ -16,6 +16,7 @@ solutions on our Cloud.
     - [AWS S3](./awss3.md): Subscribe to event notifications from an Amazon S3 bucket.
     - [AWS SNS](./awssns.md): Subscribe to messages from a AWS SNS topic.
     - [AWS SQS](./awssqs.md): Capture messages from an AWS SQS queue.
+- [Github](./github.md): Consume Github events as Cloudevents
 - Google Cloud
     - [Google Cloud Pub/Sub](./googlecloudpubsub.md): Receive messages from a Google Cloud Pub/Sub topic.
     - [Google Cloud Storage](./googlecloudstorage.md): Capture change notifications from a Google Cloud Storage bucket.