reset Decoder's state to recover from broken input

[gfx]

Decoder's state breaks if it tries to decode broken inputs, and there's no way to recover. This PR resets the state in initialization.

This will mitigate #160.

[codecov-commenter]

Codecov Report

Merging #173 (5295681) into main (afd1885) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #173   +/-   ##
=======================================
  Coverage   98.12%   98.12%           
=======================================
  Files          15       15           
  Lines         960      961    +1     
  Branches      207      207           
=======================================
+ Hits          942      943    +1     
  Misses         18       18           

Impacted Files	Coverage Δ
src/Decoder.ts	99.17% <100.00%> (+<0.01%)	⬆️
src/Encoder.ts	97.98% <100.00%> (ø)

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