add tonal example

packages/tonal/README.md

@@ -7,3 +7,28 @@ This package adds tonal / harmonic functions to strudel Patterns.
 ```sh
 npm i @strudel.cycles/tonal --save
 ```
+
+## Example
+
+```js
+import { sequence } from '@strudel.cycles/core';
+import '@strudel.cycles/tonal';
+
+const pattern = sequence(0, [1, 2]).scale('C major');
+
+const events = pattern.firstCycle().map((e) => e.show());
+```
+
+yields:
+
+```js
+(0/1 -> 1/2, 0/1 -> 1/2, C3)
+(1/2 -> 3/4, 1/2 -> 3/4, D3)
+(3/4 -> 1/1, 3/4 -> 1/1, E3)
+```
+
+[play with @strudel.cycles/tonal codesandbox](https://codesandbox.io/s/strudel-tonal-example-rgc5if?file=/src/index.js)
+
+## Tonal API
+
+See "Tonal API" in the [Strudel Tutorial](https://strudel.tidalcycles.org/tutorial/)