feat: enhance API Reference documentation and create / root endpoint

[naineel1209]

closes #4497

[server]

• created root endpoint / with a helpful response and a direct link to the documentation for the user

[clients]

• enhanced the documentation at the endpoint https://docs.polar.sh/api to improve clarity and provide the user with next steps
• enhanced the feedback section to include links for GitHub issues and the discord server for easy success

[vercel]

@naineel1209 is attempting to deploy a commit to the polar-sh Team on Vercel.

A member of the Team first needs to authorize it.

[naineel1209]

hi @birkjernstrom, could you please take a look at this?

[birkjernstrom]

Very nice @naineel1209 – thank you for this 🙏🏼 Looks great at first glance; I'll test it locally before approving & merging.