Feature: Allow selecting default file on open

**Is your feature request related to a problem? Please describe.**
I regularly use lazygit in neovim. Most of the times, I want to see the status of currently opened file, but opening lazygit highlights the first modified file by default. It doesn't even support vim motions, hence it always becomes frustrating to go to desired fle.

**Describe the solution you'd like**
Using CLI interface, allow providing a default file selection.
This is the minimum requirement, however I would like the cli interface to grow and cover more options.

**Describe alternatives you've considered**
No alternative.

**Additional context**
Not possible using custom commands.