Detect if any test has been added in the skippedTests section of xctestplan or xcscheme files

Suggest to use `XCTSkip("reason for disabling the tests and/or URL to the issue/ticket about it")` instead of `skippedTests `

Start by locating the Danger plugin code that inspects xctestplan or xcscheme files, then trace how entries in the skippedTests section are currently handled. Confirm the expected behavior for a test using XCTSkip("reason for disabling the tests and/or URL to the issue/ticket about it"); done means the check detects skippedTests entries and guides contributors toward XCTSkip instead.

Written by the indexing model from the issue text.