feat: Support non-string parameter

[TwiN]

Summary

With this, it will now be possible to skip type conversion when passing a parameter to go-color.

Before:

// Because functions took a string as parameter, you 
// first had to convert the parameter to a string.
println(color.InRed(strconv.Itoa(123)))

After:

println(color.InRed(123))

Checklist

• Tested and/or added tests to validate that the changes work as intended, if applicable.
• Added the documentation in README.md, if applicable.