feat: Allow Tag to support custom bg and text color via xss (#981)

src/components/Tag.stories.tsx

@@ -23,6 +23,7 @@ export function NoIcon() {
       <div css={Css.wPx(200).$}>
         <Tag text="Tag text that will truncate as it is too long." />
       </div>
+      <Tag text="Custom color" xss={Css.bgPurple200.$} />
     </div>
   );
 }

src/components/Tag.tsx

@@ -2,7 +2,7 @@ import { Icon, IconKey } from "src/components";
 import { Css, Margin, Only, Xss } from "src/Css";
 import { useTestIds } from "src/utils";
 
-type TagXss = Margin;
+type TagXss = Margin | "backgroundColor" | "color";
 export type TagType = "info" | "caution" | "warning" | "success" | "neutral";
 interface TagProps<X> {
   text: string;