Add two new user options for changing the final prompt character (default '$')
1) 'BULLETTRAIN_PROMPT_ROOT' - allow the user to choose if they want the final prompt character to change to '#' for root user.
2) 'BULLETTRAIN_PROMPT_CHAR' - allow the user to choose their own final prompt character (instead of '$') as long as it's length is a single character
This also changes the color of the prompt character, red for root, green for normal user, and could be expanded in the future for user selectable color choices.
Add a user selectable option 'BULLETTRAIN_DIR_EXTENDED' to show extended directory/path information. Currently this is fixed at truncating the path shown at 3 folders deep, but could be modified to support user selectable nesting/truncation.
Add an option 'BULLETTRAIN_GIT_STATUS' to allow user to show extended git repo status; e.g. added, modified, deleted files instead of just clean/dirty.
