Create docs release type

[jmgilman]

Create a docs release type that deploys documentation built by a target to AWS S3. It uses the following inputs:

• AWS S3 bucket name to publish to
• Optional prefix path to use in the bucket
• Whether to enable per-branch documentation or not

Since the setup phase already includes support for authenticating with AWS, additional authentication information is not required. The flow of the release is as follows:

• Run the configured target
• Validate artifacts are produced
• (Optional) Append the current branch name to the path if per-branch documentation is enabled
• Upload all artifacts (using their relative file path and the bucket prefix) to AWS S3