New chat rules

We restricted access to the chat. Now everyone can view it, but only registered members can post messages. We will use this oportunity to also establish some rules for the chat:

- Respect others. ChessBomb has multinational audience, and different people may root for different players.

- No insults. No swearing. No profanity.

- The official language of the chat is English. Occasionally posting in another language is fine, but don't overdo it.

We don't have real-time moderation yet, but will ban accounts from the chat for repeatedly violating these rules.

P.S. The bug which caused the chat to lag (and also slow the rest of the site) should hopefully be fixed now.