Implement Hull Moving Average (HMA) Strategy

[cinar]

Implement the Hull Moving Average (HMA) trading strategy using the existing trend.Hma indicator.

Location: strategy/trend/hma_strategy.go

Strategy Rules:

• Buy Action: Current price crosses above the Hull Moving Average.
• Sell Action: Current price crosses below the Hull Moving Average.
• Hold Action: Otherwise.

Implementation Details:

• Follow the strategy.Strategy interface.
• Use trend.NewHmaWithPeriod() or allow custom parameters.
• Provide unit tests with historical data in strategy/trend/testdata/hma_strategy.csv.
• Ensure 100% test coverage.