feature: warn user when multiple languages are detected IO-52

[pedrocodacy]

Scope

For each coverage report file, the coverage reporter will:

• look through the files that are referenced in the report and extract its language by looking at file extensions
• if there are many languages, it will pick the first one and report all coverage as that language

This is problematic since it is not visible to the users (they just call our script) and it is possible that a report contains results for multiple languages.

If you set the -l parameter it will override this behavior, but you must send the same report multiple times, one per language.

This PR

When we make the decision to pick a specific language, we now output:

• that it is happening,
• in what file,
• what other languages were detected, and
• a link to the relevant documentation.