Add initial READMEs for cache and world servers.

Author: atom0s

cache/README.md

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+<div align="center">
+    <img width="200" src="https://github.com/atom0s/XiPackets/raw/main/repo/icon.png" alt="XiPackets">
+    </br>
+</div>
+
+# Cache Server
+
+The `cache` server, often referred to as the `search` server, is responsible for game traffic that may require a longer time to return a response. Unlike the `world` server which uses UDP for its traffic, the `cache` server transmits its traffic on a separate socket, using TCP.
+
+The `cache` server is responsible for the following:
+
+  - **Auction House**
+    - Auction History
+    - Auction Lists
+  - **Search**
+    - List: Linkshell Members
+    - List: Party / Alliance Members
+    - List: Search (`/sea`, `/sea all`, etc.)
+    - Search Comments

world/README.md

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+<div align="center">
+    <img width="200" src="https://github.com/atom0s/XiPackets/raw/main/repo/icon.png" alt="XiPackets">
+    </br>
+</div>
+
+# World Server
+
+The `world` server, often referred to as the `game` server, is the server responsible for handling the main gameplay traffic for a given zone, or set of zones. On retail servers, the `world` server instances are clustered for an entire server (ie. `Asura`) where each zone is ran on its own instance. This allows retail to take individual zones offline for emergency maintenance. 
+
+Through IP and port monitoring, it has been observed that retail generally clusters zones together based on the type of zone, such as cities will run on individual `world` server instances within a single server hosted on the same port.
+
+The `world` server is responsible for all other traffic not already handled by the `cache` and `lobby` servers.
+
+## Documentation Layout
+
+The `world` server documentation is broken into two separate main categories:
+
+  - `client` - Contains packet information about packets sent by the client to the server.
+  - `server` - Contains packet information about packets sent by the server to the client.
+
+Within these folders, each packet will be separated into its own folder and have its own `README.md` file. This allows each packet to contain additional resources and information all contained within its own folder, making it easer to find, read and reference.