[Feature Request] Also color variables

For example if I'm doing

```javascript
const mycolor = '#f00';
console.log(mycolor); // this should be red.
```

or

```javascript
const obj = {
mycolor : '#f00'
}
console.log(obj.mycolor) //this should be red color
```

Look at the color parsing and highlighting logic in the atom-pigments package, likely in the lib/ directory. Understand how it currently detects color literals in code. Then extend that logic to also identify variables and object properties that hold color values. Test by modifying the package and checking if the examples in the issue display in red.

由索引模型根據 Issue 內容生成。