fix: update custom button component docs to include borderRadii

documentation/docs/fundamentals/components/custom-components.md

@@ -71,3 +71,35 @@ const Button = ({onPress, label, ...rest}: Props) => {
   );
 };
 ```
+
+Note: Make sure to update your `theme.tsx` file to include `borderRadii` properties for this custom component to work:
+
+```tsx
+import {createTheme} from '@shopify/restyle';
+
+const palette = {
+  purpleLight: '#8C6FF7',
+  purplePrimary: '#5A31F4',
+  purpleDark: '#3F22AB',
+
+  greenLight: '#56DCBA',
+  greenPrimary: '#0ECD9D',
+  greenDark: '#0A906E',
+
+  black: '#0B0B0B',
+  white: '#F0F2F3',
+};
+
+const theme = createTheme({
+  // ...rest of your theme code
+  borderRadii: {
+    s: 8,
+    m: 16,
+    l: 100,
+    xl: 40,
+  },
+});
+
+export type Theme = typeof theme;
+export default theme;
+```