Add branch to example

Author: simonw

README.md

@@ -22,13 +22,14 @@ You will need a GitHub OAuth token with full repository access.
 The easiest way to create one of these is using [https://github.com/settings/tokens](https://github.com/settings/tokens)
 
 ```python
-from github_contents import GitubContents
+from github_contents import GithubContents
 
 # For repo simonw/disaster-data:
 github = GithubContents(
     "simonw",
     "disaster-data",
-    GITHUB_OAUTH_TOKEN
+    token=GITHUB_OAUTH_TOKEN,
+    branch="main"
 )
 ```
 To read a file: