Also, new Chrome now exposes a new type in its protocol - binary.
It becomes a raw C++ array once used through C++ bindings, but for
us it's still a base64 string.
Previously protocol.d.ts was generated on `npm run tsc`. This was inconvenient because it meant that vscode checking was wrong until type checking was run manually, and was inefficient because it necessarily regenerated the types even if no new Chromium was downloaded. This patch generates the types when npm install is run from the github checkout, assuming a new Chromium revision was downloaded.
This uses the `/json/protocol` endpoint to generate type definitions for the protocol.
Currently it is lacking protocol events and commands, but I will add those later.
