Restore search functionality by indexing content in JSON files

[dan-niles]

Changes:

• Add support to index content from zimui JSON files in the ZIM using custom IndexData
• Index title and description of all videos and playlists

Close #224

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 28 lines in your changes missing coverage. Please review.

Project coverage is 1.54%. Comparing base (bf12db2) to head (435dadb).

Files	Patch %	Lines
scraper/src/youtube2zim/scraper.py	0.00%	28 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #265 +/- ## ======================================== - Coverage 1.58% 1.54% -0.04% ======================================== Files 11 11 Lines 1075 1102 +27 Branches 160 162 +2 ======================================== Hits 17 17 - Misses 1058 1085 +27 ```

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[dan-niles]

I fixed the two comments in 435dadb. I squashed and rebased with the new changes in the main branch.