Support ilst metadata and 3GPP metadata

[sunfish-shogi]

Related to #7 #13

[codecov-io]

Codecov Report

Merging #57 (6e2154e) into master (ab0af33) will increase coverage by 0.51%.
The diff coverage is 90.12%.

@@            Coverage Diff             @@
##           master      #57      +/-   ##
==========================================
+ Coverage   81.17%   81.69%   +0.51%     
==========================================
  Files          14       14              
  Lines        1594     1661      +67     
==========================================
+ Hits         1294     1357      +63     
- Misses        171      174       +3     
- Partials      129      130       +1     

Impacted Files	Coverage Δ
marshaller.go	79.78% <50.00%> (ø)
read.go	58.51% <81.81%> (+2.04%)	⬆️
mp4.go	80.00% <88.46%> (+7.27%)	⬆️
box_types.go	91.54% <95.12%> (+0.27%)	⬆️
box_info.go	77.19% <100.00%> (+0.40%)	⬆️

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