Better visible colours in avit for Ubuntu terminal

Make some colours in the avit theme bold for better visibility in the
default Ubuntu terminal theme.

themes/avit.zsh-theme

@@ -8,6 +8,7 @@ PROMPT2='%{$fg[$CARETCOLOR]%}◀%{$reset_color%} '
 
 RPROMPT='$(_vi_status)%{$(echotc UP 1)%}$(_git_time_since_commit) $(git_prompt_status) ${_return_status}%{$(echotc DO 1)%}'
 
+local _current_dir="%{$fg_bold[blue]%}%3~%{$reset_color%} "
 local _return_status="%{$fg_bold[red]%}%(?..⍉)%{$reset_color%}"
 local _hist_no="%{$fg[grey]%}%h%{$reset_color%}"