per-directory-history: redo README for Oh My Zsh

Closes #7726

plugins/per-directory-history/README.md

-[Per-Directory-History][6]
-=========================
+per-directory-history plugin
+----------------------------
 
-Per directory history for zsh, as well as global history, and the
-ability to toggle between them with ^G.
+This plugin adds per-directory history for zsh, as well as a global history,
+and the ability to toggle between them with a keyboard shortcut. This is a
+bundle of the [official plugin by @jimhester][5].
 
-This is a implementation of per directory history for zsh, some
-implementations of which exist in bash[1][],[2][].  It also implements
-a per-directory-history-toggle-history function to change from using the
-directory history to using the global history.  In both cases the history is
-always saved to both the global history and the directory history, so the
-toggle state will not effect the saved histories.  Being able to switch
-between global and directory histories on the fly is a novel feature as far
-as I am aware.
+To use it, add `per-directory-history` to the plugins array in your zshrc file:
 
-This is a standalone repository for the script, however it is also included in
-[oh-my-zsh][4] as a plugin.
+```zsh
+plugins=(... per-directory-history)
+```
 
-----------------------------------------------------------------------------
-Usage
-----------------------------------------------------------------------------
+This is an implementation of per-directory history for zsh, some implementations
+of which exist in bash[1][],[2][]. It also implements a toggle-history function
+to change from using the directory history to using the global history. In both
+cases the history is always saved to both the global history and the directory
+history, so the toggle state will not effect the saved histories. Being able to
+switch between global and directory histories on the fly is a novel feature.
 
-1.  Load this script into your interactive ZSH session:
+## Usage
 
-        % source zsh-per-directory-history.zsh
+The default mode is per directory history, interact with your history as normal.
 
-2.  The default mode if per directory history, interact with your history as normal.
+Press ^G (the <kbd>Control</kbd> and <kbd>G</kbd> keys simultaneously) to toggle
+between local and global histories. If you would prefer a different shortcut to
+toggle set the `PER_DIRECTORY_HISTORY_TOGGLE` environment variable.
 
-3.  Press ^G (the Control and G keys simultaneously) to toggle between local
-    and global histories.  If you would prefer a different shortcut to toggle
-    set the PER_DIRECTORY_HISTORY_TOGGLE environment variable.
+## Configuration
 
--------------------------------------------------------------------------------
-Configuration
--------------------------------------------------------------------------------
+* `HISTORY_BASE` is a global variable that defines the base directory in which the
+  directory histories are stored (default `$HOME/.directory_history`).
+* `per-directory-history-toggle-history` is the function to toggle between local
+  and global histories.
+* `PER_DIRECTORY_HISTORY_TOGGLE` is the key binding used to run the toggle-history
+  function above (default `^G`)
 
-* HISTORY_BASE a global variable that defines the base directory in which the
-  directory histories are stored
-* per-directory-history-toggle-history is the function to toggle the history
-
--------------------------------------------------------------------------------
-History
--------------------------------------------------------------------------------
+## History
 
 The idea/inspiration for a per directory history is from [Stewart MacArthur][1]
-and [Dieter][2], the implementation idea is from [Bart Schaefer][3].  The
-implementation is by [Jim Hester][5] in September 2012.
+and [Dieter][2], the implementation idea is from [Bart Schaefer][3]. The
+implementation is by [Jim Hester][4] in September 2012.
 
 [1]: http://www.compbiome.com/2010/07/bash-per-directory-bash-history.html
 [2]: http://dieter.plaetinck.be/per_directory_bash
 [3]: https://www.zsh.org/mla/users/1997/msg00226.html
-[4]: https://github.com/robbyrussell/oh-my-zsh
-[5]: http://jimhester.com
-[6]: https://github.com/jimhester/per-directory-history
-
+[4]: https://jimhester.com
+[5]: https://github.com/jimhester/per-directory-history