Implement std::error::Error for all error types that implement Display

[kajacx]

I added an Error impl for all errors that implement Display. I am planning on making another pull request that implements Display and Error for the remaining errors later.

[Robbepop]

@kajacx Hey, thank you this is great! I usually forget to add this trait implementation because in no_std mode it is currently unavailable. However, this is hopefully changing very soon.

It would be great if you could add the trait impls for the missing error types, too.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.48%. Comparing base (5ef1e8d) to head (e20e51a).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1089   +/-   ##
=======================================
  Coverage   80.48%   80.48%           
=======================================
  Files         270      270           
  Lines       25080    25080           
=======================================
  Hits        20186    20186           
  Misses       4894     4894           

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[Robbepop]

I will merge this PR so you can do the planned Display and Error impls in a follow-up PR if you like. :)
Thanks again for your contribution!