Dual MA Crossover

This script does the following:
1. We define the indicator with the name “Dual MA Crossover” and set it to overlay on the chart.
2. Two user inputs are created for the fast and slow moving average lengths, with default values of 10 and 100 respectively.
3. We calculate the simple moving averages (SMA) using the `ta.sma()` function.
4. The moving averages are plotted on the chart using different colors.
5. Crossover and crossunder conditions are detected using `ta.crossover()` and `ta.crossunder()` functions.
6. Labels are created at the crossover points:
• A “BUY” label is placed below the candle when the fast MA crosses above the slow MA.
• A “SELL” label is placed above the candle when the fast MA crosses below the slow MA.
7. The labels are set to have white text as requested, with green background for buy signals and red for sell signals.