Add github stack support

### Is your feature request related to a problem? Please describe.
No issues

### Describe the solution you'd like
Would like to see integration of gh stacks feature in lazy git.

### Describe alternatives you've considered
The alternative is the cli. Thats ok, this feature will be cool.

### Additional context
https://github.github.com/gh-stack/
Cool feature that gh finally added.
I know its not native git, but I think the majority are using gh so it will effect most people.

No file, test, or entry point is named in the issue. Start by reading the linked gh-stack documentation and defining which behavior lazygit should support; done means the agreed GitHub stack workflow is integrated and verified with appropriate tests.

Written by the indexing model from the issue text.