Add github package (#32)

* Add github package

* Docs

* Feedback

* Accidentally added extra

* Allow octokit to be extended

* Respond to feedback

* Feedback

packages/github/README.md

@@ -0,0 +1,47 @@
+# `@actions/github`
+
+> A hydrated Octokit client.
+
+## Usage
+
+Returns an [Octokit SDK] client. See https://octokit.github.io/rest.js for the API.
+
+```
+const github = require('@actions/github');
+
+// This should be a token with access to your repository scoped in as a secret.
+const myToken = process.env.GITHUB_TOKEN
+
+const octokit = new github.GitHub(myToken)
+
+const pulls = await octokit.pulls.get({
+    owner: 'octokit',
+    repo: 'rest.js',
+    pull_number: 123,
+    mediaType: {
+      format: 'diff'
+    }
+})
+
+console.log(pulls)
+```
+
+You can also make GraphQL requests:
+
+```
+const result = await octokit.graphql(query, variables)
+```
+
+Finally, you can get the context of the current action:
+
+```
+const github = require('@actions/github');
+
+const context = github.context
+
+const newIssue = await octokit.issues.create({
+  ...context.repo,
+  title: 'New issue!',
+  body: 'Hello Universe!'
+})
+```