feat: add raw decoder

[muktihari]

The idea is to allow us to use a minimal viable decoder for performance and memory-critical situations, where every computation or memory usage is constrained. RawDecoder itself is using constant memory < 131 KB and the Decode method has zero heap alloc (except errors) while it may use additional small stack memory. The implementation of the callback function is also expected to have minimal overhead. Theoretically, from the memory usage alone, this can run on an embedded device, for instance, using tinygo or other compilers, but no attempt has been made.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (82b5514) 99.89% compared to head (784fb24) 99.89%.

Additional details and impacted files

@@           Coverage Diff            @@
##           master      #96    +/-   ##
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  Coverage   99.89%   99.89%            
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  Files          42       43     +1     
  Lines        3839     3965   +126     
========================================
+ Hits         3835     3961   +126     
  Misses          4        4            

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