Donchian Channel Breakout Strategy added. Issue 338

[whencanibe]

Describe Request

Implements the Donchian Channel Breakout Strategy as requested in issue #338.

The Donchian Channel indicator already exists in the volatility package.
This PR adds the strategy layer on top of it, following the existing patterns in strategy/volatility.

Fixed #338

Change Type

New strategy.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 97.61905% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 93.21%. Comparing base (0ec4196) to head (9ffcc79).

Files with missing lines	Patch %	Lines
strategy/volatility/volatility.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #361      +/-   ##
==========================================
+ Coverage   93.18%   93.21%   +0.02%     
==========================================
  Files         218      219       +1     
  Lines        6269     6311      +42     
==========================================
+ Hits         5842     5883      +41     
- Misses        346      347       +1     
  Partials       81       81              

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[cinar]

Thank you very much for the contribution! I am unable to merge it as your commit is not signed. If you can sign your commit through your GPG key, the system will let me to merge it.