Add Coinbase OnchainKit Fund Button to Home Page

[homanp]

This pull request integrates the Coinbase OnchainKit Fund Button into our Next.js application's home page. Here's a summary of the changes:

1. Added @coinbase/onchainkit as a dependency in package.json.
2. Updated app/layout.tsx to include OnchainKit styles and wrap the application with the Providers component.
3. Modified app/page.tsx to import and render the FundButton component on the home page.

Note: This PR does not include the setup of environment variables or the creation of a providers.tsx file. These steps should be completed separately to ensure full functionality of the OnchainKit integration.

To complete the integration, please follow these additional steps:

1. Create a .env file in the project root with the following content:

   NEXT_PUBLIC_ONCHAINKIT_API_KEY=YOUR_CLIENT_API_KEY
   NEXT_PUBLIC_CDP_PROJECT_ID=YOUR_CDP_PROJECT_ID
   

   Replace YOUR_CLIENT_API_KEY and YOUR_CDP_PROJECT_ID with your actual values.

2. Create a providers.tsx file in the app directory with the following content:

   'use client';
   import { OnchainKitProvider } from '@coinbase/onchainkit';
   import { base } from 'wagmi/chains';
   
   export function Providers({ children }: { children: React.ReactNode }) {
     return (
       <OnchainKitProvider
         apiKey={process.env.NEXT_PUBLIC_ONCHAINKIT_API_KEY!}
         projectId={process.env.NEXT_PUBLIC_CDP_PROJECT_ID!}
         chain={base}
       >
         {children}
       </OnchainKitProvider>
     );
   }

These changes add the basic functionality of the Fund Button to the home page. Further customization of the button's appearance or behavior can be done as needed.