rework the execution part

Author: pthmas

.vitepress/config.ts

@@ -210,10 +210,7 @@ function sidebarHome() {
         },
         {
           text: "Execution",
-          collapsed: true,
-          items: [
-            { text: "ABCI", link: "/learn/execution/abci" },
-          ],
+          link: "/learn/execution"
         },
         {
           text: "Resources",

learn/execution.md

@@ -0,0 +1,40 @@
+# Execution Layers in Rollkit
+
+Rollkit is designed to be modular and flexible, allowing different execution layers to be plugged in via the ABCI (Application Blockchain Interface) protocol. Rollkit defines a general-purpose execution interface ([see execution.go](https://github.com/rollkit/rollkit/blob/main/core/execution/execution.go)) that enables developers to integrate any compatible application as the rollup's execution layer.
+
+This means you can use a variety of ABCI or Reth compatible applications as the execution environment for your rollup.
+
+## Supported Execution Layers
+
+### ABCI-Compatible Execution Layers
+
+Any ABCI-compatible application can be used as the execution layer for a Rollkit rollup. This flexibility allows developers to choose the best execution environment for their use case, whether it's a custom application or an existing framework.
+
+A common example is a Cosmos SDK-based application, which provides a rich set of modules for staking, governance, IBC, and more, and is widely used in the Cosmos ecosystem.
+
+- [Cosmos SDK Documentation](https://docs.cosmos.network/)
+- [Cosmos SDK ABCI Documentation](https://docs.cosmos.network/main/build/abci/introduction)
+- [Rollkit ABCI Adapter](https://github.com/rollkit/go-execution-abci)
+
+### Reth
+
+Reth is a high-performance Ethereum execution client written in Rust. Rollkit can integrate Reth as an execution layer, enabling Ethereum-compatible rollups to process EVM transactions and maintain Ethereum-like state. This allows developers to build rollups that leverage the Ethereum ecosystem, tooling, and smart contracts, while benefiting from Rollkit's modular consensus and data availability.
+
+For more information about Reth, see the official documentation:
+
+- [Reth GitHub Repository](https://github.com/paradigmxyz/reth)
+- [Rollkit Reth Integration](https://github.com/rollkit/lumen)
+
+## How It Works
+
+- Rollkit acts as the consensus and data availability layer.
+- The execution layer (Cosmos SDK app or Reth) processes transactions and maintains application state.
+- Communication between Rollkit and the execution layer happens via the ABCI protocol or other supported interfaces.
+
+## Benefits
+
+- **Modularity:** Choose the execution environment that best fits your use case.
+- **Interoperability:** Leverage existing Cosmos SDK modules, deploy CosmWasm smart contracts, or use EVM tooling with Reth.
+- **Extensibility:** Easily upgrade or swap out the execution layer as your rollup evolves.
+
+For more details on integrating an execution layer with Rollkit, see the respective documentation links above.