Implement Slider v2 Component

[traviskaufman]

• Continuous Slider
• Discrete Slider

@sgomes already doing some work on this.

Notes

Step values need to be able to be quantized to decimal places, e.g. min = 0, max = 5, step = .2. Possible algorithm: Take the raw value, divide it by step, round that number, and then multiply the original step value by the rounded number. E.g.

function quantize(val, min, max, step) {
  const numSteps = Math.round(val / step);
  const quantizedVal = numSteps * step;
  return Math.max(min, Math.min(max, quantizedVal));
}

const min = 0, max = 5, step = .2;
quantize(3.56, min, max, step); // 3.6
quantize(2.148692, min, max, step) // 2.2
quantize(1.061733, min, max, step) // 1

[sfdexter]

Superceded by material-components/material-components-web#25