Small fixes / additions on the media player

[Kurami32]

Description
Continuation of #1166
I worked on the dev/0.8.4 branch.

According to the contributing guide, A PR should contain:

• A clear description of why it was opened.
• A short title that best describes the change.
• Must pass unit and integration tests, which can be run checked locally prior to opening a PR.
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Additional Details
Before add the metadata on the audio player I organized a bit the file, added some comments, fixed some issues on the media player and added the "fallback image" on the audio player but without the metadata yet (I let some things commented for work later there), so~ right now all the audio previews look like this:

I updated the translation for spanish too.

[Kurami32]

Hmm... I don't modified nothing from backend. I only cloned the 0.8.4 branch and made changes there.

[gtsteffaniak]

adjusted the display to be centered , otherwise it looks good to me. I'll merge if you have no other changes

[Kurami32]

adjusted the display to be centered , otherwise it looks good to me. I'll merge if you have no other changes

Thanks! And for now I don't have other changes, you can merge this. I'm still figuring how to implement the metadata.

[gtsteffaniak]

great! I'll keep an eye out for any other PRs