Add flutter plugin (#8150)

plugins/flutter/README.md

+## Flutter plugin
+
+The Flutter plugin provides completion and useful aliases
+
+To use it, add flutter to the plugins array of your zshrc file:
+
+```
+plugins=(... flutter)
+```
+
+## Aliases
+
+| Alias      | Command                | Description                                                                |
+| :--------- | :--------------------- | :------------------------------------------------------------------------- |
+| `fl`       | `flutter`              | Shorthand for flutter command                                              |
+| `flr`      | `flutter run`          | Runs flutter app                                                           |
+| `fldoc`    | `flutter doctor`       | Runs flutter doctor                                                        |
+| `flb`      | `flutter build`        | Build flutter application                                                  |
+| `flattach` | `flutter attach`       | Attaches flutter to a running flutter application with enabled observatory |
+| `flget`    | `flutter packages get` | Installs dependencies                                                      |
+| `flc`      | `flutter clean`        | Cleans flutter porject                                                     |

plugins/flutter/_flutter

+#compdef flutter
+#autoload
+
+local -a _1st_arguments
+_1st_arguments=(
+  "analyze":"Analyze the project's Dart code."
+  "assemble":"Assemble and build flutter resources."
+  "attach":"Attach to a running application."
+  "build":"Flutter build commands."
+  "channel":"List or switch flutter channels."
+  "clean":"Delete the build/ and .dart_tool/ directories."
+  "config":"Configure Flutter settings."
+  "create":"Create a new Flutter project."
+  "devices":"List all connected devices."
+  "doctor":"Show information about the installed tooling."
+  "drive":"Runs Flutter Driver tests for the current project."
+  "emulators":"List, launch and create emulators."
+  "format":" Format one or more dart files."
+  "help":"Display help information for flutter."
+  "install":"Install a Flutter app on an attached device."
+  "logs":"Show log output for running Flutter apps."
+  "make-host-app-editable":"Moves host apps from generated directories to non-generated directories so that they can be edited by developers."
+  "precache":"Populates the Flutter tool's cache of binary artifacts."
+  "pub":"Commands for managing Flutter packages."
+  "run":"Run your Flutter app on an attached device."
+  "screenshot":"Take a screenshot from a connected device."
+  "test":"Run Flutter unit tests for the current project."
+  "upgrade":"Upgrade your copy of Flutter."
+  "version":"List or switch flutter versions."
+)
+
+_arguments -C '*:: :->subcmds'
+
+if (( CURRENT == 1 )); then
+  _describe -t commands "flutter command" _1st_arguments
+  return
+fi

plugins/flutter/flutter.plugin.zsh

+alias fl="flutter"
+alias flr="flutter run"
+alias fldoc="flutter doctor"
+alias flb="flutter build"
+alias flattach="flutter attach"
+alias flget="flutter packages get"
+alias flc="flutter clean"