adding beta feature links

Author: sbvegan

pages/builders/chain-operators/configuration/rollup.mdx

@@ -971,6 +971,10 @@ instead of the older output oracle mechanism.
 
 ### Custom Gas Token
 
+The Custom Gas Token configuration lets OP Stack chain operators deploy their 
+chain allowing a specific ERC-20 token to be deposited in as the native token 
+to pay for gas fees. Learn more [here](/stack/protocol/features/custom-gas-token).
+
 ***
 
 #### useCustomGasToken
@@ -998,6 +1002,11 @@ gas on L2.
 
 ### Alt-DA Mode
 
+Alt-DA Mode enables seamless integration of various Data Availability (DA) 
+Layers, regardless of their commitment type, into the OP Stack. This allows 
+any chain operator to launch an OP Stack chain using their favorite DA Layer 
+for sustainably low costs. Lean more [here](/stack/protocol/features/alt-da-mode).
+
 ***
 
 #### usePlasma