add litecord voice server protocol (lvsp) draft

docs/README.md

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+# Internal documentation
+
+The Litecord Voice Server Protocol (LVSP) is documented here.

docs/lvsp/00-connection.md

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+# Litecord Voice Server Protocol (LVSP)
+
+LVSP is a protocol for Litecord to communicate with an external component
+dedicated for voice data. The voice server is responsible for the
+Voice Websocket Discord and Voice UDP connections.
+
+LVSP runs over a websocket with TLS. The encoding is JSON.
+
+## High level
+
+In a high level:
+ - Litecord connects to the Voice Server via a URL already configured
+    beforehand.
+ - 
+
+## OP code table
+
+"client" is litecord. "server" is the voice server.
+
+**TODO:** voice state management.
+
+| opcode | name | sent by |
+| --: | :-- | :-- |
+| 0 | HELLO | server |
+| 1 | IDENTIFY | client |
+| 2 | RESUME | client |
+| 3 | READY | server |
+| 4 | HEARTBEAT | client |
+| 5 | HEARTBEAT\_ACK | server |
+
+## high level overview
+
+ - connect, receive HELLO
+ - send IDENTIFY or RESUME
+ - receive READY
+ - start HEARTBEAT'ing
+
+## HELLO message
+
+Sent by the server when a connection is established.
+
+| field | type | description |
+| --: | :-- | :-- |
+| heartbeat\_interval | integer | amount of milliseconds to heartbeat with |
+
+## IDENTIFY message
+
+Sent by the client to identify itself.
+
+| field | type | description |
+| --: | :-- | :-- |
+| token | string | secret value kept between client and server |
+
+## RESUME message
+
+Sent by the client to resume itself from a failed websocket connection.
+
+The server will resend its data, then send a READY message.
+
+| field | type | description |
+| --: | :-- | :-- |
+| token | string | same value from IDENTIFY.token |
+| seq | integer | last sequence number to resume from |
+
+## READY message
+
+**TODO**
+
+| field | type | description |
+| --: | :-- | :-- |
+
+## HEARTBEAT message
+
+Sent by the client as a keepalive / health monitoring method.
+
+The server MUST reply with a HEARTBEAT\_ACK message back in a reasonable
+time period.
+
+**TODO**
+
+| field | type | description |
+| --: | :-- | :-- |
+
+## HEARTBEAT\_ACK message
+
+Sent by the server in reply to a HEARTBEAT message coming from the client.
+
+**TODO**
+
+| field | type | description |
+| --: | :-- | :-- |