adk deploy: handle non-python dependencies (npx, typescript mpcs, etc)

I've deployed my agent to Google Cloud Run using `adk deploy`.
But now, I find that `npx` (used for a MCP Tool) was not installed; and even if it was, the mcp typescript server I was using will be downloaded and installed every time the Cloud Run Backend is restarted.

I think we could add 'external' (non python) deps [easily into the Dockerfile](https://github.com/google/adk-python/blob/c04adaade118be242fcf110e24e96253ac6550ab/src/google/adk/cli/cli_deploy.py#L23) by just having a new `requirements.sh` that will be ran if present; like [what we're doing](https://github.com/google/adk-python/blob/c04adaade118be242fcf110e24e96253ac6550ab/src/google/adk/cli/cli_deploy.py#L176-L192) with `requirements.txt`

If you think this makes sense, I could send a PR

Thanks