Consider sourcing prompt function into .bashrc

[hulbert]

@erikbryant pointed me to this article about startup file loading order for bash https://medium.com/@rajsek/zsh-bash-startup-files-loading-order-bashrc-zshrc-etc-e30045652f2e

In README presently setup step is to source into ~/.bash_profile but this doesn't seem to work for a tool we have which spawns a child shell as that is a non-login shell that appends to the PS1 already set which contains an invocation of prompt_git:

dotfiles/bash_prompt.sh

Line 104 in 3577458

PS1+="\$(prompt_git "" \"\[${blue}\]\")"; # Git repository details