feat(isHexColor): support css colors level 4 spec (#1233)

Author: acconrad

src/lib/isHexColor.js

@@ -1,6 +1,6 @@
 import assertString from './util/assertString';
 
-const hexcolor = /^#?([0-9A-F]{3}|[0-9A-F]{6})$/i;
+const hexcolor = /^#?([0-9A-F]{3}|[0-9A-F]{4}|[0-9A-F]{6}|[0-9A-F]{8})$/i;
 
 export default function isHexColor(str) {
   assertString(str);

test/validators.js

@@ -2588,14 +2588,16 @@ describe('Validators', () => {
     test({
       validator: 'isHexColor',
       valid: [
+        '#ff0000ff',
         '#ff0034',
         '#CCCCCC',
+        '0f38',
         'fff',
         '#f00',
       ],
       invalid: [
         '#ff',
-        'fff0',
+        'fff0a',
         '#ff12FG',
       ],
     });