format_version (required): Tells Chrome which version of the manifest format to use. Right now there is only one version, and it is version 1. (NOTE: Maybe we should just remove this, we can always add a format_version key later if needed).id (required): A unique ID for the extension. Right now, this can be any 40 digit hexadecimal number, but in the future it will be a SHA-1 hash of the extension