Highlight paragraph while its audio recording is being played

[nya-elimu]

Relates to #5
Relates to #21
Relates to #64

[gscdev]

@nya-elimuai How to combine paragraph highlighting with word highlighting?

[nya-elimu]

@nya-elimuai How to combine paragraph highlighting with word highlighting?

@gscdev Good question. I think paragraph highlighting would only make sense when we use audio recordings instead of Text-to-Speech. Maybe by setting a gray background color for the entire paragraph or something similar? However, I suggest we postpone adding this feature until we figure out how to do word-by-word highlighting for audio recordings, which will be our upcoming task.

So instead of this issue, I suggest #58 as the issue to tackle next.