fix(ios): set type attribute for captured audio

[ath0mas]

Platforms affected

iOS

Motivation and Context

Capturing audio is returning a mediaDictionary without its type attribute.

Description

1. getMediaDictionaryFromPath should always set type for returned fileDict, either using "type" param or determined from file
2. audio type should not be forced to "audio/wav"

Testing

If "type" param is forced, returned fileDict uses it too.
And then, do capture audio on iOS to have an object with filled mimeType determined from file, usually "audio/x-wav".

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[erisu]

Code changes LGTM.
Also tested the code changes in a sample project.