docs: Explain the root namespace (#1241)

docs/pages/world/world-101.mdx

@@ -22,7 +22,7 @@ A World contains resources. Currently, there exists three types of resources. Mo
 2. **Table**: a [Store](store) table. Used to store and retrieve data.
 3. **System**: a piece of logic, stored as EVM bytecode. Systems have no state, and instead read and write to Tables.
 
-Each resource is contained within a namespace. You can think of the resources within a World as a filesystem:
+Each resource is contained within a namespace (possibly the ROOT one, where you use an empty string for the namespace). You can think of the resources within a World as a filesystem:
 
 ```bash
 root
@@ -36,11 +36,18 @@ root
     | Drop <- System
     | Score <- Table
     | Win <- System
+| Counter <- Table
+| Increment <- System
 ```
 
 The organization of resources within namespaces is used for two different features of MUD:
 
-1. **Access control:** resources in a namespace have “write” access to the other resources within their namespace. Currently, having write access only matters for systems interacting with tables: it means these systems can create and edit records within those tables.
+1. **Access control:** resources in a namespace have “write” access to the other resources within their namespace.
+   Currently, having write access only matters for systems interacting with tables: it means these systems can create and edit records within those tables.
+
+   Note that systems in the ROOT namespace are able to bypass access control.
+   Because they are called with `DELEGATECALL`, they can bypass any hooks and write directly to any table in the `World`.
+
 2. **Synchronization of state**: MUD clients can decide which namespaces they synchronize. Synchronization means different things depending on the resource type:
    - **Synchronizing a Table** means downloading and keeping track of all changes to records found within the Table. As an example, synchronizing a `BalanceTable` would mean keeping track of the balances of all addresses within that table.
    - **Synchronizing a System** means downloading its EVM bytecode from the chain, and in a future version of MUD, being able to execute these systems optimistically client side. As an example, this would allow clients to immediately predict the likely outcome of an on-chain action without relying on external nodes or services like Tenderly to simulate the outcome.
@@ -75,6 +82,7 @@ Systems **MUST** use the `_msgSender()` function exposed in the `System` interfa
 There exists two types of systems:
 
 1. **Regular systems**: Regular systems are `CALL`ed from the World, which isolates their storage from the World storage. They read and write to the Store by going through the World, which does access control checks (eg: Can this system write to this table>). Regular systems can register namespaced function selectors on the World. eg: `World.myNamespace_ExampleSystem_createRecord()`.
+
 2. **Root systems**: Root systems are `DELEGATECALL`ed from the World, which lets them borrow the World storage. They read and write to the Store _directly_. There are _NO_ access control on Root systems. Root systems can register root function selectors, allowing their functions to be called on the World directly, eg: `World.createRecord()`.
 
 Systems are not root by default, only systems registered in the ROOT namespace (the empty string namespace: `""`) are treated as root systems.