feat(zsh): add prompt config (#5)

* fix(zsh): use zsh extsn and host env var

* feat(zsh): add prompt config

zsh/.zsh/45-prompts.zsh

···
+autoload -Uz vcs_info
+precmd() {
+    vcs_info
+}
+
+zstyle ':vcs_info:*' enable git
+zstyle ':vcs_info:git:*' formats '%b '
+
+setopt PROMPT_SUBST
+PROMPT='%F{blue}%n%f@%F{blue}%m%f %B%2~%b %F{blue}${vcs_info_msg_0_}%f%# '

zsh/.zshrc

···
 unset F
 
 # Load custom stuff from a host-specific zshrc (if marked executable)
-[[ -x ~/.$HOSTNAME.zshrc ]] && source ~/.$HOSTNAME.zshrc
+[[ -x $HOME/.${HOST}.zshrc ]] && source $HOME/.${HOST}.zshrc