refactor(osx): Rename osx plugin to macos (#10341)

Apple changed the name of their operating system from OS X to macOS a number of years ago. This was overdue!

As per issue  #10311

* refactor(osx): rename `osx` plugin to `macos`
* refactor(macos): Add symbolic link from old `osx` plugin name.

plugins/macos/README.md

@@ -0,0 +1,63 @@
+# MacOS plugin
+
+This plugin provides a few utilities to make it more enjoyable on macOS (previously named OSX).
+
+To start using it, add the `macos` plugin to your plugins array in `~/.zshrc`:
+
+```zsh
+plugins=(... macos)
+```
+
+Original author: [Sorin Ionescu](https://github.com/sorin-ionescu)
+
+## Commands
+
+| Command       | Description                                              |
+| :------------ | :------------------------------------------------------- |
+| `tab`         | Open the current directory in a new tab                  |
+| `split_tab`   | Split the current terminal tab horizontally              |
+| `vsplit_tab`  | Split the current terminal tab vertically                |
+| `ofd`         | Open the current directory in a Finder window            |
+| `pfd`         | Return the path of the frontmost Finder window           |
+| `pfs`         | Return the current Finder selection                      |
+| `cdf`         | `cd` to the current Finder directory                     |
+| `pushdf`      | `pushd` to the current Finder directory                  |
+| `pxd`         | Return the current Xcode project directory               |
+| `cdx`         | `cd` to the current Xcode project directory              |
+| `quick-look`  | Quick-Look a specified file                              |
+| `man-preview` | Open a specified man page in Preview app                 |
+| `showfiles`   | Show hidden files in Finder                              |
+| `hidefiles`   | Hide the hidden files in Finder                          |
+| `itunes`      | _DEPRECATED_. Use `music` from macOS Catalina on         |
+| `music`       | Control Apple Music. Use `music -h` for usage details    |
+| `spotify`     | Control Spotify and search by artist, album, track…      |
+| `rmdsstore`   | Remove .DS_Store files recursively in a directory        |
+| `btrestart`   | Restart the Bluetooth daemon                             |
+| `freespace`   | Erases purgeable disk space with 0s on the selected disk |
+
+## Acknowledgements
+
+This application makes use of the following third party scripts:
+
+[shpotify](https://github.com/hnarayanan/shpotify)
+
+Copyright (c) 2012–2019 [Harish Narayanan](https://harishnarayanan.org/).
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.