Add another 'simple' theme

- Add rkitover/sh-prompt-simple theme

Signed-off-by: Joe Block <jpb@unixorn.net>

README.md

@@ -1963,6 +1963,7 @@ If you're using [Antigen](https://github.com/zsh-users/antigen), you can test th
 - [simpalt](https://github.com/m-lima/simpalt) - An information-rich small-footprint theme for ZSH based on [Agnoster](https://github.com/agnoster/agnoster-zsh-theme).
 - [simple (daopengz)](https://github.com/DaopengZ/simple-zsh-theme) - Works well with both light and dark terminal themes. Includes `vcs`, `username` and `path` decorations.
 - [simple (pavdmyt)](https://github.com/pavdmyt/simple-oh-my-zsh-theme) - Minimalist theme based on [robbyrussel](https://github.com/ohmyzsh/ohmyzsh/wiki/Themes#robbyrussell) that embeds `git` status information in iTerm's window title bar instead of using space in the prompt.
+- [simple (rkitover)](https://github.com/rkitover/sh-prompt-simple) - A simple, lightweight, and nice looking prompt that runs quickly even in very slow shells like MSYS2, Cygwin and WSL. It shows decorations for the short name of the current environment (distribution, OS, etc.) the `git` branch when in a `git` checkout, as well as the last command exit status (green checkmark for success and red X mark for non-zero exit.)
 - [simple (savecoders)](https://github.com/Savecoders/simpleTheme-zsh-theme) - Simple and minimalist theme with `git`, `username` and execution status decorations.
 - [simple (tourcoder)](https://github.com/tourcoder/simple.zsh-theme) - Minimalist prompt, includes `git` status decorations.
 - [simple (yhiraki)](https://github.com/yhiraki/zsh-simple-prompt) - Minimal prompt, doesn't require special fonts.