Export Decoder and Encoder for direct usage

[sergeyzenchenko]

In some cases Decoder/Encoder need to be used directly without wrapper functions. For example in our project we have custom format that consist of
binary with:

• number
• number
• array
• number
• binary

and this structure can't be parsed or formed using regular functions, but it can be easily done by using Decoder/Encoder directly.

[sergeyzenchenko]

@gfx what do you think about it?

[codecov-io]

Codecov Report

Merging #45 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #45      +/-   ##
==========================================
+ Coverage   91.46%   91.48%   +0.02%     
==========================================
  Files          14       14              
  Lines         808      810       +2     
  Branches      170      170              
==========================================
+ Hits          739      741       +2     
  Misses         49       49              
  Partials       20       20

Impacted Files	Coverage Δ
src/index.ts	100% <100%> (ø)	⬆️

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[gfx]

The reason why they are not exported is just their interfaces are not stable yet and there are no use cases suggested, but if you need them, it's time to export them.

LGTM

[sergeyzenchenko]

thanks!