isColor does not detect capitalized RGB(A) and HSL(A) functions

[bartveneman]

• Webpack Version: N/A
• Operating System (or Browser): Mac OS 10.14.3
• Node Version: 10.15.2
• postcss-values-parser Version: 3.0.0 (🎉)

How Do We Reproduce?

const {parse} = require('postcss-values-parser')

const fixtures = [
  'RGBA(100, 200, 11, .5)',
  'RGB(100, 200, 11)',
  'Hsl(20, 10%, 5%)',
  'HSLA(20, 10%, 5%, 0.5)'
]

fixtures.forEach(color => {
  parse(color, {loose: true}).walk(node => {
    console.log(node.isColor)
  })
})

Expected Behavior

Expected isColor to be true for all of these cases

Actual Behavior

isColor is false for all of these cases

Related issues and code

• Related to #67

I hope I've covered most cases by now 😬