Add support for all hex color notations (#866) (#867)

Author: nesty92

regexes.go

@@ -10,7 +10,7 @@ const (
 	numericRegexString               = "^[-+]?[0-9]+(?:\\.[0-9]+)?$"
 	numberRegexString                = "^[0-9]+$"
 	hexadecimalRegexString           = "^(0[xX])?[0-9a-fA-F]+$"
-	hexColorRegexString              = "^#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6})$"
+	hexColorRegexString              = "^#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{4}|[0-9a-fA-F]{6}|[0-9a-fA-F]{8})$"
 	rgbRegexString                   = "^rgb\\(\\s*(?:(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])|(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%)\\s*\\)$"
 	rgbaRegexString                  = "^rgba\\(\\s*(?:(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])|(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%\\s*,\\s*(?:0|[1-9]\\d?|1\\d\\d?|2[0-4]\\d|25[0-5])%)\\s*,\\s*(?:(?:0.[1-9]*)|[01])\\s*\\)$"
 	hslRegexString                   = "^hsl\\(\\s*(?:0|[1-9]\\d?|[12]\\d\\d|3[0-5]\\d|360)\\s*,\\s*(?:(?:0|[1-9]\\d?|100)%)\\s*,\\s*(?:(?:0|[1-9]\\d?|100)%)\\s*\\)$"