Update DA docs

Author: pthmas

learn/data-availability.md

@@ -2,15 +2,15 @@
 
 Data availability (DA) is a core component of Rollkit's modular rollup framework. In Rollkit, data availability ensures that all transaction data and block information required to verify the rollup's state is accessible to anyone running a node or light client.
 
+Learn more about data availability:
+
+- [What is DA](https://celestia.org/what-is-da/)
+- [The importance of DA for Rollups](https://medium.com/zeeve/exploring-data-availability-layer-and-its-importance-in-rollups-0a4fbf2e0ffc)
+
 ## How Rollkit Handles Data Availability
 
 Rollkit is designed to be DA-agnostic, meaning it can integrate with different data availability layers depending on your needs. The main options are:
 
-- **Mock Data Availability (Mock DA):**
-  - Simple in-memory DA layer that is great for testing and development.
-  - Data is stored and served by the rollup node itself.
-  - Not secure for production, as data can be withheld by the node operator.
-
 - **Local Data Availability (Local DA):**
   - Used for development, testing, and local deployments.
   - Not secure for production, as data can be withheld by the node operator.
@@ -26,12 +26,10 @@ Rollkit is designed to be DA-agnostic, meaning it can integrate with different d
   - Rollkit rollups rely on data availability to enable fraud proofs and ensure that invalid state transitions can be challenged.
   - If data is unavailable, users cannot verify the rollup's state or submit fraud proofs.
 
-- **Interoperability:**
-  - By supporting multiple DA layers, Rollkit enables rollups to be deployed in a variety of environments, from local devnets to scalable, decentralized networks.
-
 ## Best Practices
 
-- **Use Mock or Local DA only for development and testing.**
+- **Use Local DA only for development and testing locally.**
+- **Alternatively, you can use [Celestia testnets](https://docs.celestia.org/how-to-guides/participate).**
 - **For production, always use a decentralized DA layer that implements the Rollkit DA interface.**
 
 ## Learn More