[Feature Request] Ability to reinitialize alien_theme without restarting zsh

[alextremblay]

Is your feature request related to a problem? Please describe.
This feature request is related to #30

Describe the solution you'd like
I'd love to find some way to reinitialize alien_theme without having to kill my current shell, edit .zshrc, and start a new shell

Describe alternatives you've considered
N/A

Additional context
To give some context, I predominantly access zsh through terminal emulators configured to use powerline-enabled fonts, including nerd fonts, but I sometimes launch new shells and access existing shells (through tmux) from a terminal emulator that can't support powerline (terminals integrated into IDEs, for example), or through SSH from terminal emulators on machine's I can't install custom fonts on