Top level flag to specify directory to operate in

### Describe the feature or problem you’d like to solve

For example your org has N number of projects you have cloned locally where N may be more then 100. To list all PRs on all projects you need to repeatedly access each project and run `gh pr list` for N times.

Unwanted scenario:
```
cd
gh pr list
cd ..
# Repeat N times
```

### Proposed solution

It would be nice to have such key in to level flags such `--dir`, `--repo` or `--project-path` to have such operation possible:

```
for proj in $(ls); do gh --project-path=$rpoj pr list; done
```
or to have kind of `.ghrc` where someone could list all current projects (configuration file in YAML, JSON, or INI format )

It would be helpful for DevOps teams they usually have to deal with all projects at the same time.

从 issue 中描述的提议的顶层 `gh` 标志和 `gh pr list` 命令开始。将 `--dir`、`--repo` 和 `--project-path` 这几个替代方案与提议的 `.ghrc` 配置方案进行比较；只有在明确规定一种方案并定义其在各个本地项目中的行为后，工作才算完成。

由索引模型根据 Issue 内容生成。