Add instructions for testnet2 deployment ops (#31)

Part of [Create a public laconicd testnet](https://www.notion.so/Create-a-public-laconicd-testnet-896a11bdd8094eff8f1b49c0be0ca3b8)

- Add instructions to setup stage2 laconicd deployment
- Add instructions for stage1 to stage2 migration
- Add a script and instructions for users to upgrade their nodes to testnet stage2

Reviewed-on: cerc-io/testnet-laconicd-stack#31
Co-authored-by: Prathamesh Musale <prathamesh.musale0@gmail.com>
Co-committed-by: Prathamesh Musale <prathamesh.musale0@gmail.com>

README.md

@@ -10,6 +10,7 @@ Stacks to run a node for laconic testnet
 
 - [Update deployments after code changes](./ops/update-deployments.md)
 - [Halt stage0 and start stage1](./ops/stage0-to-stage1.md)
+- [Halt stage1 and start stage2](./ops/stage1-to-stage2.md)
 - [Create deployments from scratch (for reference only)](./ops/deployments-from-scratch.md)
 - [Deploy and transfer new tokens for nitro operations](./ops/nitro-token-ops.md)
 
@@ -17,6 +18,10 @@ Stacks to run a node for laconic testnet
 
 Follow steps in [testnet-onboarding-validator.md](./testnet-onboarding-validator.md) to onboard your participant and join as a validator on the LORO testnet
 
+## SAPO testnet
+
+Follow steps in [Upgrade to SAPO testnet](./testnet-onboarding-validator.md#upgrade-to-sapo-testnet) for upgrading your LORO testnet node to SAPO testnet
+
 ## Run testnet Nitro Node
 
 Follow steps in [testnet-nitro-node.md](./testnet-nitro-node.md) to run you Nitro node for the testnet