Extend Neopixelbus to support SK6812 'White Chip' and WWA.

**Describe the problem you have/What new integration you would like**

Add support for SK6812 White chip and WWA as seen at the bottom on their [product listing](https://www.btf-lighting.com/pages/led-chips-contrast)

**Please describe your use case for this integration and alternatives you've tried:**

A solution could possible be having two new variants `SK6812_WHITE` and `SK6812_WWA` for these chips.
```yaml
light:
- platform: neopixelbus
name: "NeoPixel Light"
pin: GPIO23
num_leds: 60
variant: SK6812_WHITE or SK6812_WWA
```

**Additional context**

Limited testing shows that both chips are reacting to data from this configuration.
```yaml
light:
- platform: neopixelbus
name: "NeoPixel Light"
pin: GPIO23
num_leds: 60
variant: SK6812
type: BRGW
```
[https://www.btf-lighting.com/pages/led-chips-contrast](https://www.btf-lighting.com/pages/led-chips-contrast)

Start by reviewing the existing neopixelbus SK6812 configuration and the linked product listing for the White chip and WWA variants. Verify that the proposed SK6812_WHITE and SK6812_WWA values work with the shown YAML configuration and cover both chip types.

Written by the indexing model from the issue text.