feat: support audio in quizzes

[huyenltnguyen]

Checklist:

• I have read and followed the contribution guidelines.
• I have read and followed the how to open a pull request guide.
• My pull request targets the main branch of the repo.
• I have tested these changes locally on my machine.

This PR:

• Adds support for audio in quiz questions (ref: feat(client,challenge-parser): support audio and transcript in quiz questions freeCodeCamp#65711)
• Is related to https://github.com/freeCodeCamp/language-curricula/issues/4

Note: There are currently no quizzes in prod with audio. The Language Curricula team is starting to add audio to English quizzes, but these quizzes are not yet available in prod (isUpcomingChange: true). This change is purely preparatory, but it is required in order to release the quizzes. Otherwise, quizzes will reference audio that doesn't exist in the mobile app.

Screenshot

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Steps to test

Since there are no quiz challenges with audio in staging or prod, I used mock challenge data to test.

You can:

• Revert 4b89805 to bring back the test code
• Start the app
• Go to A2 Spanish and pick any quiz challenge
• Scroll down to question 2

[huyenltnguyen]

I'm adding a new QuizAudio class so I renamed EnglishAudio to EnglishScene, to better differentiate the two.

[huyenltnguyen]

Implemented a shared class so both scene and quiz audio can share audio logic. (I did try to make the scene and quiz audio schema as close as possible for this purpose).