[discussion] Drop Swift 5.3 support

[417-72KI]

Suggestion

• Make current version (v3.12.3) to be a last support for Swift 5.3
• Require Swift 5.4 for next release (v3.12.4 or v3.13.0).
• Soon, create a new release ( v3.12.5, v3.13.0 or v3.13.1 ) and make it to require Swift 5.5.

Motivation

There is an issue and workaround for building Danger-Swift in Swift 5.3 Docker image (#375, #426).

Fortunately, I tried to run swift build --disable-sandbox -c release in Swift 5.4 image and succeeded!
I think that supporting Swift 5.3 is no longer necessary.

Additionally, dropping Swift 5.4 is more happier for CI because

• Xcode 13.3 requires macOS monterey
• macOS monterey runner in GitHub Actions doesn't have Xcode 12.x (https://github.com/actions/virtual-environments/blob/main/images/macos/macos-12-Readme.md#xcode)
  • it means Swift 5.4 is not supported in macOS monterey runner.

[f-meloni]

Thank you for writing this issue :)
I'm totally OK with dropping Swift 5.3, and wait a little bit before dropping Swift 5.4, Ideally I would wait for the new Xcode major to come out and then drop that as well :)

[417-72KI]

Thank you for reactions!
I will make a PR to prepare dropping 5.3 only and open a new issue for 5.4 🚀