Add FAQ

[MatthewWid]

Add a Frequently Asked Questions (FAQ) section to the documentation with answers to questions that frequently reappear such as:

• [ ] How does server-sent events work?
• [ ] Is this the same thing as server push?
• [ ] How do I disconnect a session from the server?
• [ ] How do I track a user across multiple sessions or tabs?
• [ ] How do I push an event to a specific user?
• [x] How do I batch-send multiple events at once?
• [ ] How do I add metadata to a session or a channel?
• [ ] Why am I getting the error "Cannot push data to a non-active session."?
• [ ] Why am I getting the error "Cannot register a non-active session."?