Fix: Issues with Initial Project Run

[ugurkellecioglu]

Thank you for the project. I tried it out and noticed that some improvements could be made to help others run the project more easily.

In this PR, I have introduced a .env.template file so that newcomers can easily understand which API keys are required to get started right away.

Additionally, the public stream key was defined inline in every file. I have changed it to be a public environment variable.

Finally, if someone logs in via Google, Next.js throws an error, "Google's hostname must be included in the Next.js configuration". So I included google's hostname that they use for storing profile pictures in next config.