Adding some "Getting started" section or page

[dret]

hello! i am trying to get started with setting up my own AIP infrastructure. i started with the site-generator because it seemed like the logical place to start: set up the machinery, and then worry about feeding in some things to publish. the current README does not really help with how to get the thing up and running, so i am proposing to add this information.

[dret]

it seems like https://google.aip.dev/contributing has (some of) that info, so maybe just linking there would be an easy initial fix. i'll report back on how well these instructions are working for me.

[dret]

it seems like https://google.aip.dev/contributing#development-environment was written before the repo was split into a content part and a code part. it says "If you have Docker installed, clone this repository and run the serve.sh file at the root of the repository", and there is a serve.sh file in the content repo, but there must be some dependency on the code repo, right?