Add YouTube fields parsing and refactoring

[mikhail-vl]

1. Allows to parse YouTube RSS: https://www.youtube.com/feeds/videos.xml?channel_id=UCQadniwbukI6ZmTN2oTTb-g
2. Adds additional fields for media:thumbnail, media:content, media:description.
3. Refactoring.

[codecov]

Codecov Report

Merging #31 (2a4d108) into main (80662bf) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main       #31   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           13        15    +2     
  Lines          178       189   +11     
  Branches        35        39    +4     
=========================================
+ Hits           178       189   +11     

Impacted Files	Coverage Δ
src/api/api.ts	100.00% <100.00%> (ø)
src/components/QueryEditor/QueryEditor.tsx	100.00% <100.00%> (ø)
src/constants/datasource.ts	100.00% <100.00%> (ø)
src/constants/index.ts	100.00% <100.00%> (ø)
src/constants/items.ts	100.00% <100.00%> (ø)
src/constants/query.ts	100.00% <100.00%> (ø)

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[mikhail-vl]

Looks good!