Support include file and Add GithubToken

87ee5d8 supports following format about `include`
.gitconfig
```
[include]
  path = .gitconfig.local
```

.gitconfig.local
```
[user]
  name = sona-tar
```

4c81a02 supports following format about `github.token`, and then It need will not be set `GITHUB_TOKEN` on ghr.
```
[github]
 token = aaaaaaaaaaaaaaaaaaaaaaaaaa
```
Related Pull Request.
[Support github.token in gitconfig by sona-tar · Pull Request #8 · tcnksm/ghr](https://github.com/tcnksm/ghr/pull/8)