Feature Request: Swift Package Manager support #7047

What language does this apply to?
If it's a proto syntax change, is it for proto2 or proto3? N/A
If it's about generated code change, what programming language? N/A

Describe the problem you are trying to solve.
I am trying to convert a repository from CocoaPods to Swift Package Manager, but this dependency doesn't support it.

Describe the solution you'd like
I would like this repository to have a Package.swift file to support Swift Package Manager.

Describe alternatives you've considered

1. I have considered using something instead of Protobuf, but it currently works in the repository.
2. Additionally, I have considered not converting to Swift Package Manager, but it seems more practical than CocoaPods.
3. Finally, I have considered attempting to implement this myself, but picking out the correct source files proved to be difficult.

Additional context
Add any other context or screenshots about the feature request here.