docs(readme): added example

Author: meszaros-lajos-gyorgy

Diff for: README.md

@@ -2,12 +2,75 @@
 
 This code monkey patches AudioParams with a method to get values at any time
 
-## install
+## Getting started
+
+### Install
 
 `npm i audioparam-getvalueattime`
 
+### Example
+
+
+```javascript
+import 'audioparam-getvalueattime'
+
+// if you interrupt a schedulement with cancelAndHoldAtTime,
+// then you can continue from there with new events, e.g. ramps
+// but if there was nothing scheduled, then it will try to run your ramp from
+// the end of a last event
+const properCancelAndHold = (node, time) => {
+  if (node.hasScheduledChangesAtTime(time)) {
+    node.cancelAndHoldAtTime(time)
+  } else {
+    const valueAtTime = node.getValueAtTime(time)
+    node.setValueAtTime(valueAtTime, time)
+  }
+}
+
+const ctx = new AudioContext()
+const volume = ctx.createGain()
+const oscillator = ctx.createOscillator()
+
+// ...
+
+const attack = 0.1
+const release = 0.3
+
+const scheduleNoteOn = (pitch, velocity, t) => {
+  const gain = volume.gain
+  const frequency = oscillator.frequency
+  properCancelAndHold(gain, t)
+  gain.linearRampToValueAtTime(velocity, t + attack)
+  frequency.setValueAtTime(pitch, t)
+}
+
+const scheduleNoteOff = (t) => {
+  const gain = volume.gain
+  properCancelAndHold(gain, t)
+  gain.linearRampToValueAtTime(0, t + release)
+}
+
+// ...
+
+const startTime = ctx.currentTime
+
+scheduleNoteOn(440, 0.5, startTime)
+scheduleNoteOff(startTime + 1)
+
+scheduleNoteOn(550, 0.5, startTime + 2)
+scheduleNoteOff(startTime + 3)
+
+scheduleNoteOn(660, 0.5, startTime + 2.5)
+scheduleNoteOff(startTime + 3.5)
+
+```
+
 ## API
 
+The lib has no exports, since it's an IIFE, that will automatically run and patch up the native AudioContext
+
+The following methods will become available on AudioParam instances:
+
 `AudioParam.prototype.getValueAtTime(t)` - calculates the value at `t` time based on scheduled changes
 
 `AudioParam.prototype.hasScheduledChangesAtTime(t)` - checks whether there are any changes scheduled at or after `t` time