Add interactive code samples

@alexandratran commented on [Tue Jan 17 2023](https://github.com/MetaMask/mm-docs-v2/issues/14)

Use CodeSandbox to display interactive code samples. This might take the place of the example button implementations in the legacy site, for example see [Accessing Accounts](https://docs.metamask.io/guide/accessing-accounts.html), [Connecting to MetaMask](https://docs.metamask.io/guide/getting-started.html#connecting-to-metamask), and [Sending Transactions](https://docs.metamask.io/guide/sending-transactions.html#example).

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@vandan commented on [Tue Apr 04 2023](https://github.com/MetaMask/mm-docs-v2/issues/14#issuecomment-1496344887)

Next step would be to fully set up CodeSandbox with a set of global dependencies.

- [ ] Set up template with all dependencies we want in a new repository
- [ ] Provide a readme that links to the template and provides guidelines for adding a codeblock with new external dependencies
- [ ] Add a set of initial runnable examples (at least parity with legacy site as described above)