Function multiplyOpacity

multiplyOpacity(colour: Colourish, amt: number): string
Returns a variation of colour with its opacity multiplied by amt. Value will be clamped to 0..1
```
// Return a colour string for blue that is 50% opaque
multiplyOpacity(`blue`, 0.5);
// eg: `rgba(0,0,255,0.5)`

// Returns a colour string that is 50% more opaque
multiplyOpacity(`hsla(200,100%,50%,50%`, 0.5);
// eg: `hsla(200,100%,50%,25%)`
```
Named colours
Parameters
- colour: Colourish
  A valid CSS colour
- amt: number
  Amount to multiply opacity by
Returns string
String representation of colour