Add error for out of bounds chars

[ionite34]

• Added error to be propagated to DecodeError on out of bound characters
• Added associated tests

[codecov]

Codecov Report

Merging #10 (689cb75) into main (b45dc12) will increase coverage by 0.26%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #10      +/-   ##
==========================================
+ Coverage   94.34%   94.60%   +0.26%     
==========================================
  Files           3        3              
  Lines         106      111       +5     
==========================================
+ Hits          100      105       +5     
  Misses          6        6              

Flag	Coverage Δ
pytest	94.60% <100.00%> (+0.26%)	⬆️
rust-llvm-cov	94.60% <100.00%> (+0.26%)	⬆️

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Impacted Files	Coverage Δ
src/encoder.rs	94.45% <100.00%> (+0.33%)	⬆️

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