Add notes and instructions for connecting app to Github Repo

[MargaretcZhang]

Step by step instructions for user to connect app to Github Repo
Location: should be listed as sub page under Portal-> apps

e.g.
create a repo in the org thats mapped to your spice account
with the same name as one of your spice apps
then in spice app settings there's an option to install the spice app to github
then you can connect that repo to the app