Add Swift Package Manager Support

[alejandro-all-win-software]

DESCRIPTION

• Added SPM support for both iOS & MacOS plugins.
• Closes [Feature request] Add Swift Package Manager support #322

[tony-voyager]

@alejandro-all-win-software @CaiJingLong Can you review and merge this PR to support swift package manager?

[Goolpe]

@alejandro-all-win-software
I have issue with flutter pub get:

Resolving dependencies...
Error on line 1, column 7: "name" field doesn't match expected name "flutter_image_compress".
  ╷
1 │ name: flutter_image_compress_workspace
  │       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  ╵
Failed to update packages.

I tried to rename in pubspec.yaml to flutter_image_compress_workspace

But import has next problem:
"Target of URI doesn't exist: 'package:flutter_image_compress_workspace/flutter_image_compress.dart'.
Try creating the file referenced by the URI, or try using a URI for a file that does exist."

Tried
'package:flutter_image_compress/package:flutter_image_compress.dart'
'package:flutter_image_compress_workspace/package:flutter_image_compress.dart' - same issue

[alejandro-all-win-software]

Hey @Goolpe, sorry for the late reply. I'm not sure how that issue is related to this PR, since I only added support for SwiftPM.