New support for multiple format poster images

[KANE-99]

Accept multiple images for setting background poster image for video.

[codecov-io]

Codecov Report

Merging #396 (3ef2f4d) into master (df63f7f) will increase coverage by 0.08%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #396      +/-   ##
==========================================
+ Coverage   47.96%   48.04%   +0.08%     
==========================================
  Files          47       47              
  Lines        1280     1282       +2     
==========================================
+ Hits          614      616       +2     
  Misses        666      666              

Impacted Files	Coverage Δ
src/components/PosterImage.js	80.00% <100.00%> (+5.00%)	:arrow_up:

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