Add rgb to rgba util

src/renderer/utils/index.ts

@@ -6,3 +6,4 @@ export * from './title-case';
 export * from './get-header-color';
 export * from './parse-search-params';
 export * from './format-duration-string';
+export * from './rgb-to-rgba';

src/renderer/utils/rgb-to-rgba.ts

@@ -0,0 +1,7 @@
+export const rgbToRgba = (rgb: string | undefined, alpha: number) => {
+    if (!rgb) {
+        return undefined;
+    }
+
+    return rgb.replace(')', `, ${alpha})`).replace('rgb', 'rgba');
+};