[Chore] make newline and trailing whitespaces suggestions more clear

Description

Problem: danger suggestions for trailing whitespaces and end-of-file newlines aren't very clear because they are rendered similarly and the output error message only mentions the former. This makes it a bit hard to understand that only a newline is missing for example.

Solution: improve danger's output failure message as well as the comments that it leaves with suggestions.

Related issue(s)

None

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