docs(encoding): add many more examples to mod.ts

[johnpyp]

This PR adds many more examples to encoding's front-page mod.ts.

Each example uses assertEquals to ensure correctness and testability.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.22%. Comparing base (b5a5fe4) to head (863999c).
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6570   +/-   ##
=======================================
  Coverage   95.21%   95.22%           
=======================================
  Files         577      577           
  Lines       43381    43381           
  Branches     6487     6487           
=======================================
+ Hits        41307    41308    +1     
+ Misses       2034     2033    -1     
  Partials       40       40           

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[kt3k]

LGTM. Nice! Thanks