Make bash available on Windows

[kit494way]

There are several bash environments available on Windows, including MSYS2's bash, Git Bash, and w64devkit's bash.
This change makes these bash available in navi.

Config.yaml settings for using Git Bash.

shell:
  command: "\"C:/Program Files/Git/bin/bash.exe\""
  finder_command: "C:/Program Files/Git/bin/bash.exe"
  forward_slash_path: true

Before:

After:

[alexis-opolka]

I'll take a look at it during the week, thanks. ^-^

[denisidoro]

LGTM, but I'll let Alexis merge it

[alexis-opolka]

Sorry for the wait, it also LGTM, I just had a quick question about the paths handling.