[fastlane_core] [env] Add Swift version to fastlane env

[minuscorp]

Checklist

• I've run bundle exec rspec from the root directory to see all new and existing tests pass
• I've followed the fastlane code style and run bundle exec rubocop -a to ensure the code style is valid
• I've read the Contribution Guidelines
• I've updated the documentation if necessary.

Motivation and Context

It is good to know beforehand the Swift version used when a Fastlane.Swift and other issues may arise instead of having to ask the user for it.

Description

I've added a new row with the swift version (only the version code) to the fastlane env command.

Testing Steps

1. Checkout this branch and install it
2. Run fastlane env
3. 🚀

[crazymanish]

Tested! It's working on my mac! 🎉

[joshdholtz]

Love this! Kinda embarrassed we didn’t have this earlier 😛 But thank you!

[fastlane-bot]

Hey @minuscorp 👋

Thank you for your contribution to fastlane and congrats on getting this pull request merged 🎉
The code change now lives in the master branch, however it wasn't released to RubyGems yet.
We usually ship about once a week, and your PR will be included in the next one.

Please let us know if this change requires an immediate release by adding a comment here 👍
We'll notify you once we shipped a new release with your changes 🚀

[fastlane-bot]

Congratulations! 🎉 This was released as part of fastlane 2.185.0 🚀