Add input field on hello-pluts-react-final UI to build blockfrost provider

[EehMauro]

Update the current "Hello plu-ts" example react repos and docs

Acceptance criteria

• [x] Update the instructions on the documentation repo (if necessary)
• [x] Update the hello-pluts-react repo (Adding an input field to provide the Blockfrost API Key)
• [x] Update the hello-pluts-react-final repo (Adding an input field to provide the Blockfrost API Key)