crypto: add toChecksumAddress

[libotony]

No description provided.

[coveralls]

Pull Request Test Coverage Report for Build 27

• 16 of 16 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 97.75%

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Totals
Change from base Build 24:	0.1%
Covered Lines:	286
Relevant Lines:	288

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💛 - Coveralls

[codecov-io]

Codecov Report

Merging #6 into master will increase coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master       #6      +/-   ##
==========================================
+ Coverage   99.35%   99.38%   +0.03%     
==========================================
  Files           5        5              
  Lines         308      324      +16     
  Branches       51       54       +3     
==========================================
+ Hits          306      322      +16     
  Misses          2        2

Impacted Files	Coverage Δ
src/lib/crypto.ts	98.11% <100%> (+0.33%)	⬆️

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