macports: add README (#7204)

plugins/macports/README.md

+# Macports plugin
+
+This plugin adds completion for the package manager [Macports](https://macports.com/),
+as well as some aliases for common Macports commands.
+
+To use it, add `macports` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... macports)
+```
+
+## Aliases
+
+| Alias | Command                            | Description                                                  |
+|-------|------------------------------------|--------------------------------------------------------------|
+| pc    | `sudo port clean --all installed`  | Clean up intermediate installation files for installed ports |
+| pi    | `sudo port install`                | Install package given as argument                            |
+| psu   | `sudo port selfupdate`             | Update ports tree with MacPorts repository                   |
+| puni  | `sudo port uninstall inactive`     | Uninstall inactive ports                                     |
+| puo   | `sudo port upgrade outdated`       | Upgrade ports with newer versions available                  |
+| pup   | `psu && puo`                       | Update ports tree, then upgrade ports to newest versions     |

plugins/macports/macports.plugin.zsh

-#Aliases
 alias pc="sudo port clean --all installed"
-alias pi="sudo port install $1"
+alias pi="sudo port install"
 alias psu="sudo port selfupdate"
 alias puni="sudo port uninstall inactive"
 alias puo="sudo port upgrade outdated"
 alias pup="psu && puo"
-