Change to using arrow functions (#1603)

* Change to using arrow functions

Co-authored-by: v1b3m <vibenjamin6@gmail.com>
Co-authored-by: Matheus <matheus_benini@hotmail.com>

* Add lint rule

---------

Co-authored-by: v1b3m <vibenjamin6@gmail.com>
Co-authored-by: Matheus <matheus_benini@hotmail.com>
Co-authored-by: Charles Bochet <charles@twenty.com>

front/src/modules/ui/theme/constants/colors.ts

@@ -146,7 +146,7 @@ export const color = {
   ...secondaryColors,
 };
 
-export function rgba(hex: string, alpha: number) {
+export const rgba = (hex: string, alpha: number) => {
   const rgb = hexRgb(hex, { format: 'array' }).slice(0, -1).join(',');
   return `rgba(${rgb},${alpha})`;
-}
+};