Add an example that connects a wallet in the browser

[lorisleiva]

Create a simple React application that connects a wallet in the browser via the Solana Wallet Adapter library.

• Create a MetaplexProvider component that uses the wallet provided by the WalletProvider component and return a Metaplex instance. Here is a very rough proof of concept.
• Add dropdown to select a cluster (mainnet, devnet or testnet) and hook that dropdown with the ConnectionProvider which will end up being used by the MetaplexProvider.
• Use the connected wallet to display a random NFT from their wallet and add a "Pick a new random NFT" button to refresh it.
• Write a detailed README file that explains the steps to reproduce to achieve the created example. Look at the current READMEs for inspiration. Since this example is not about getting started with a web framework, choose a starting framework from this repository and link to its README as the first first. I recommend Next.js since it has the lowest amount of steps to get started right now.
• When writing the steps to reproduce, it is fine to add links to larger components or style sheets instead of having to explain them all in the README. Especially if the component is more here for UI proposes than for providing valuable logic.
• When styling components, try to stay consistent to the neutral style that was created in the existing examples.

[statikdev]

@lorisleiva // I can try taking this on over the weekend.

edit: just saw this is for fellowships.

[rainbow1223]

I think this project is well-structured