enabled showing number of git stashes for themes and applied the change to af-magic theme

[jacobmoroni]

Standards checklist:

• [ x] The PR title is descriptive.
• [ x] The PR doesn't replicate another PR which is already open.
• I have read the contribution guide and followed all the instructions.
• [ x] The code follows the code style guide detailed in the wiki.
• [ x] The code is mine or it's from somewhere with an MIT-compatible license.
• [ x] The code is efficient, to the best of my ability, and does not waste computer resources.
• [ x] The code is stable and I have tested it myself, to the best of my abilities.

Changes:

• in git.sh I check the stash list and if the theme variables are set, it reports the number of stashed entries in the git status
• in af-magic.sh I set the necessary variables to enable visualizing the stash
• if those are not set, this logic is ignored

Other comments:

Clean State (unchanged):

Dirty State (unchanged):

Dirty Stash state (Dirty and has a stash):

Clean Stash state (Clean and has a stash):

...

[jacobmoroni]

I think it would make sense to keep those lines in af-magic theme commented out or just not in there to not mess up other people using it. It would just be nice to add the option to view this in any theme