add Stochastic Momentum Index

[DaveSkender]

Description

Adds Stochastic Momentum Index indicator

Implements #626 and is based on the recipe depicted by William Blau in Technical Analysis of Stocks & Commodities magazine, edition 11-81 (January 1993).

Checklist

• My code follows the existing style, code structure, and naming taxonomy
• I have commented my code, particularly in hard-to-understand areas
• I have performed a self-review of my own code and included any verifying manual calculations
• I have added or updated unit tests that prove my fix is effective or that my feature works, and achieves sufficient code coverage. New and existing unit tests pass locally and in the build (below) with my changes
• My changes generate no new warnings and running code analysis does not produce any issues
• I have added or run the performance tests that depict optimal execution times
• I have made corresponding changes to the documentation

[DaveSkender]

Current implementation profile:

// usage (standard)
IEnumerable<SmiResult> results =
  quotes.GetSmi(lookbackPeriods, firstSmoothPeriods,
                 secondSmoothPeriods, signalPeriods);

Parameters

name	type	notes
lookbackPeriods	int	Lookback period (N) for the stochastic. Must be greater than 0.
firstSmoothPeriods	int	First smoothing factor lookback. Must be greater than 0.
secondSmoothPeriods	int	Second smoothing factor lookback. Must be greater than 0.
signalPeriods	int	Optional. EMA of SMI lookback periods. Must be greater than 0. Default is 3.

[github-actions]

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