Add support for color CLI arguments in new UI

[dan-niles]

Close #217

Changes:

• Add Config schema and save main-color and secondary-color in config.json
• Update Vuetify initialization to load main and secondary colors from config.json
• Update UI to support different background colors from config.json
  • secondary-color is used as the background for the ZIM UI.
  • main-color is used for the banner if a banner image is not available.

Screenshots:

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 1.58%. Comparing base (67d2a6c) to head (b5c417e).

Files	Patch %	Lines
scraper/src/youtube2zim/schemas.py	0.00%	3 Missing :warning:
scraper/src/youtube2zim/scraper.py	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #263 +/- ## ======================================== - Coverage 1.58% 1.58% -0.01% ======================================== Files 11 11 Lines 1070 1074 +4 Branches 160 160 ======================================== Hits 17 17 - Misses 1053 1057 +4 ```

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