Provide rating guide for talks

[ericpoe]

Add ratings suggestions guide when rating a talk.

From https://phpc.social/@deadlugosi/113381283906017994

Ratings suggestions:

⭐️⭐️⭐️⭐️⭐️ Fantastic talk that you endorse for future conference line-ups.
⭐️⭐️⭐️⭐️ Still great, endorsed for future events, but also feedback includes one way you think it could be taken to the next level.
⭐️⭐️⭐️ Good, but feedback includes a few things the speaker should address before next time.
⭐️⭐️ Needs more than a few improvements, maybe included some bad or outdated info; a talk that’s not ready to share.
⭐️ You’d be disappointed to see this talk on another event schedule.