Avoid showing Snapfile twice, fix not showing lanes, improvements & more

* Update README.md (#7385)
* Fix not showing the lane list and selection when not passing any arguments (#7549)
* Add "--fail-on-errors" support to Danger action (#7487)
* Updated docs description for pilot/testflight action (#7550)
* fix platform (#7360)
* [gym] Remove promotion for use_legacy_build_api (#7379)
* user_error if plist error (#7547)
* more tests for aliases (#7546)

https://github.com/fastlane/fastlane/releases/tag/2.1.0
