Update README and document Wasmi crate features

[Robbepop]

Rendered: Wasm Features

Rendered: Crate Features

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.23%. Comparing base (7949063) to head (39bcdf3).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1430      +/-   ##
==========================================
+ Coverage   71.19%   71.23%   +0.03%     
==========================================
  Files         161      161              
  Lines       16270    16270              
==========================================
+ Hits        11584    11590       +6     
+ Misses       4686     4680       -6     

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