package: add repo

Add `repo` to `package.json` for warning do not appear when installing with `clib`.
It looks this way:
```sh
$ clib install bpkg/bpkg
      fetch : https://raw.githubusercontent.com/bpkg/bpkg/master/package.json
    warning : missing repo in package.json
  info: Uninstalling /usr/local/bin/bpkg...
  info: Installing /usr/local/bin/bpkg...
```