feat: adsr documentation

docs/ADSR.md

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+Certainly! Here's an example of generating an ADSR (Attack, Decay, Sustain, Release) envelope in Python:
+
+```python
+import numpy as np
+import matplotlib.pyplot as plt
+
+# Parameters
+sample_rate = 44100  # Sample rate in Hz
+duration = 5  # Duration of the envelope in seconds
+
+# Time values
+num_samples = int(duration * sample_rate)
+time = np.arange(num_samples) / sample_rate
+
+# ADSR parameters
+attack_time = 0.5  # Attack time in seconds
+decay_time = 0.3  # Decay time in seconds
+sustain_level = 0.6  # Sustain level (0 to 1)
+release_time = 1.0  # Release time in seconds
+
+# Generate the ADSR envelope
+envelope = np.zeros(num_samples)
+attack_samples = int(attack_time * sample_rate)
+decay_samples = int(decay_time * sample_rate)
+release_samples = int(release_time * sample_rate)
+
+# Attack phase
+envelope[:attack_samples] = np.linspace(0, 1, num=attack_samples)
+
+# Decay phase
+decay_slope = (1 - sustain_level) / decay_samples
+envelope[attack_samples:attack_samples + decay_samples] = np.linspace(1, sustain_level, num=decay_samples) - decay_slope * np.arange(decay_samples)
+
+# Sustain phase
+envelope[attack_samples + decay_samples:-release_samples] = sustain_level
+
+# Release phase
+release_slope = sustain_level / release_samples
+envelope[-release_samples:] = sustain_level - release_slope * np.arange(release_samples)
+
+# Normalize the envelope
+envelope /= np.max(envelope)
+
+# Plot the envelope
+plt.plot(time, envelope)
+plt.xlabel('Time (s)')
+plt.ylabel('Amplitude')
+plt.title('ADSR Envelope')
+plt.show()
+```
+
+In this example, we specify the sample rate and duration of the envelope. We define the ADSR parameters: attack time, decay time, sustain level, and release time.
+
+We create an array to store the envelope values and initialize it with zeros. We calculate the number of samples for each phase based on the sample rate and duration.
+
+We then calculate the envelope values for each phase. The attack phase increases linearly from 0 to 1. The decay phase decreases linearly from 1 to the sustain level. The sustain phase maintains a constant value equal to the sustain level. The release phase decreases linearly from the sustain level to 0.
+
+After generating the envelope, we normalize it to ensure the maximum value is 1. Finally, we plot the envelope using Matplotlib.
+
+You can modify the ADSR parameters to create different envelope shapes or experiment with adding modulation to create more dynamic and expressive sounds.