Function detectCadence

detectCadence(from: ChordData, to: ChordData, key: KeyScale): Cadence
Classify the cadence formed by moving from one chord to the next.
- authentic: V (dominant a fifth above the tonic) to I
- plagal: IV (a fourth above the tonic) to I
- deceptive: V to the submediant (diatonic vi or borrowed bVI in major, VI in minor)
- half: any chord other than the dominant itself to V
A static V-to-V repeat with no root motion is not a cadence and yields null.
Parameters
- from: ChordData
  The penultimate chord.
- to: ChordData
  The final chord.
- key: KeyScale
  The prevailing key.
Returns Cadence
The cadence type, or null.
Example
```
import { detectCadence, makeChord, majorKey } from '@libraz/libcantus';
detectCadence(makeChord(7, 'maj'), makeChord(0, 'maj'), majorKey(0)); // => 'authentic'
```
- Defined in analyze/functional/cadence.ts:43