Added API documentation for the PSB Hosting project

Available functionality via API:

Actions with an account: authorization, receiving account data, updating profile data.

Getting a list of services, operating systems, pre-installed software

Order operations: Placing a new order, getting a list of user orders, getting an order by its ID, extending an order, changing the auto-renewal status, changing the tariff

Server operations: restarting, stopping, starting, getting action history, changing the server password, changing the server port, changing the OS, assigning IPv6

Getting a list of payments

Ticket operations: getting a list of tickets, creating a ticket, getting ticket data by its ID.

Getting ticket chat messages, sending a message to the chat.