add git-escape-magic

https://github.com/knu/zsh-git-escape-magic

"If you are a hard-core zsh user that takes extended_glob seriously for granted, you must be annoyed with git's refspec (notation to point a commit, tree, etc.) that goes like HEAD^ or blahblah~3 because the signs like [^~{}] are globbing meta-characters for zsh that require escaping to be passed through to the git command.

Here is what this tweak is about. It eliminates the need for manually escaping those meta-characters."