Add CryptoUint64

[at-wat]

Return Cryptograpic 64-bit random integer.

[codecov]

Codecov Report

Merging #2 into master will increase coverage by 25.00%.
The diff coverage is 66.66%.

@@             Coverage Diff             @@
##           master       #2       +/-   ##
===========================================
+ Coverage   60.00%   85.00%   +25.00%     
===========================================
  Files           1        2        +1     
  Lines          35       40        +5     
===========================================
+ Hits           21       34       +13     
+ Misses         12        3        -9     
- Partials        2        3        +1     

Flag	Coverage Δ
#go	85.00% <66.66%> (+25.00%)	⬆️
#wasm	85.00% <66.66%> (+25.00%)	⬆️

Impacted Files	Coverage Δ
math.go	92.30% <50.00%> (ø)
crypto.go	71.42% <71.42%> (ø)

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