docs: add architecture diagrams to ExEx documentation (#20193)

Co-authored-by: Matthias Seitz <matthias.seitz@outlook.de>

docs/vocs/docs/pages/exex/how-it-works.mdx

@@ -4,6 +4,28 @@ description: How Execution Extensions (ExExes) work in Reth.
 
 # How do ExExes work?
 
+## Architecture
+
+```mermaid
+sequenceDiagram
+    participant Reth
+    participant ExEx
+
+    Note over Reth,ExEx: Normal Flow
+    Reth->>ExEx: ChainCommit Notification
+    activate ExEx
+    ExEx->>ExEx: Process Block Data
+    ExEx->>Reth: FinishedHeight Event
+    deactivate ExEx
+
+    Note over Reth,ExEx: Reorg Flow
+    Reth->>ExEx: ChainReorg Notification
+    activate ExEx
+    ExEx->>ExEx: Rollback & Re-process
+    ExEx->>Reth: New FinishedHeight Event
+    deactivate ExEx
+```
+
 ExExes are just [Futures](https://doc.rust-lang.org/std/future/trait.Future.html) that run indefinitely alongside Reth
 – as simple as that.
 

docs/vocs/docs/pages/exex/overview.mdx

@@ -17,6 +17,27 @@ initiated by Reth.
 
 Read more about things you can build with Execution Extensions in the [Paradigm blog](https://www.paradigm.xyz/2024/05/reth-exex).
 
+## Architecture
+
+```mermaid
+graph LR
+    subgraph "Reth Process"
+        Reth[Reth Core]
+
+        Reth -->|Notifications| ExEx1[ExEx 1]
+        Reth -->|Notifications| ExEx2[ExEx 2]
+        Reth -->|Notifications| ExEx3[ExEx N]
+
+        ExEx1 -->|Events| Reth
+        ExEx2 -->|Events| Reth
+        ExEx3 -->|Events| Reth
+    end
+
+    ExEx1 --> External1[External System 1]
+    ExEx2 --> External2[External System 2]
+    ExEx3 --> External3[External System N]
+```
+
 ## What Execution Extensions are not
 
 Execution Extensions are not separate processes that connect to the main Reth node process.