Add plugin for Swift Package Manager (#5670)

* Add plugin for Swift Package Manager
* swift-package-manager: Rename plugin to 'swift-pm'

plugins/swift-pm/README.md

+# Swift Package Manager
+
+## Description
+
+This plugin provides a few utilities that make you faster on your daily work with the [Swift Package Manager](https://github.com/apple/swift-package-manager).
+
+To start using it, add the `swift-pm` plugin to your `plugins` array in `~/.zshrc`:
+
+```zsh
+plugins=(... swift-pm)
+```
+
+## Aliases
+
+| Alias | Description                         | Command                            |
+|-------|-------------------------------------|------------------------------------|
+| `spi` | Initialize a new package            | `swift package init`               |
+| `spf` | Fetch package dependencies          | `swift package fetch`              |
+| `spu` | Update package dependencies         | `swift package update`             |
+| `spx` | Generates an Xcode project          | `swift package generate-xcodeproj` |
+| `sps` | Print the resolved dependency graph | `swift package show-dependencies`  |
+| `spd` | Print parsed Package.swift as JSON  | `swift package dump-package`       |

plugins/swift-pm/swift-pm.plugin.zsh

+# Some aliases to make your life with the Swift Package Manager faster ✌️
+
+alias spi='swift package init'
+alias spf='swift package fetch'
+alias spu='swift package update'
+alias spx='swift package generate-xcodeproj'
+alias sps='swift package show-dependencies'
+alias spd='swift package dump-package'