Feature request: support parse color from rgba string

[luatnd]

I got the error:

Invalid HEX color: "rgba(0,0,0,0.2)"

After read the source code, I see this program has not supported to parse the color string from rgb

[luatnd]

I've created a pull request for that feature, can you take a look at this feature @onury ?

[manstie]

Would be nice if this supported transparency 👍