docs(score_generation): update docs to show how to amend quantization manually #310

# try quantising manually
import drumscript as ds
from drumscript.notation_generator.score_builder import build_score

# y, sr = ds.load_audio("drums.wav", sr=44100)
y, sr = ds.load_audio(AUDIO_FILE_10, sr=44100)
y = ds.normalise_audio(y)
tempo = ds.detect_tempo(y)
onsets = ds.detect_onsets(y, sr)
events = ds.classify_events(y, sr, onsets)


# Use 8th note grid (8) instead of default 16th (16)
# build_score(events, tempo, quantization_subdivision=8)
build_score(events, tempo, quantization_subdivision=4)