feat: Add extending faker by custom providers

[rodnover55]

Hello. This pull request added ability to add new tag in faker with custom providers. Existing tag cannot be rewritten

[codecov]

Codecov Report

Merging #33 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #33      +/-   ##
==========================================
+ Coverage   97.85%   97.88%   +0.02%     
==========================================
  Files           8        8              
  Lines         373      378       +5     
==========================================
+ Hits          365      370       +5     
  Misses          4        4              
  Partials        4        4

Impacted Files	Coverage Δ
faker.go	95.45% <100%> (+0.13%)	⬆️

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[bxcodec]

Very cool,

I'm curious, is this will work. I mean, if we import this package in another package, how to use it anyway?

If you don't mind, add some example how to use it in readme.md

[rodnover55]

As I see it works correctly.

I test it with this code.
Could you review example to be make sure that I tested what you want?

If all is ok, I will change readme. ;)

Thank you.

[bxcodec]

LGTM