Yuxuan captioning

[yuxuanjerrychen01]

1. Fixed local storage api and local storage display (will use default local storage if encounter local storage bugs) #153
2. Introduced transcript download feature #154
3. Adding primary preset themes divider
4. Added primary preset themes (black bg yellow text, black bg white text, blue bg yellow text, dark blue bg yellow text)
5. Fixed caption constraints #152

[ammpr]

Regarding #1- Disabling DOM storage entirely, which can be done in high security configurations breaks this. Additionally, recommend adding some sort of pop or print message informing the user that local web storage is disabled or inaccessible. Possibly even a pop that will ask for access.

Will continue to examine this. Regardless, not typical user behavior.