Support for blend modes

[mattpilott]

Yo yo yo Lukas!

I really need support for blend modes on colours, is there anyway this can be added and appended as an additional key in the fill item?

Then could be like this in the json:

{
  "color": {
    "test": {
      "0": {
        "type": "color",
        "value": "#c4c4c4ff"
      },
      "1": {
        "type": "color",
        "value": "#00000033",
        "blendMode": "overlay"
      },
      "description": "",
      "extensions": {
        "org.lukasoppermann.figmaDesignTokens": {
          "styleId": "S:89d747408eae95621c7bbf946257c1462388e8d0,",
          "exportKey": "color"
        }
      }
    }
  }
}

[mattpilott]

https://github.com/lukasoppermann/design-tokens/pull/193

Started a PR