[Docs] Fix Docker Walkthrough gateway container name and add supplier…

… staking note (#939)


- Changed incorrect `gateway-example` Docker container name to `gateway` under the **Configure and run your Gateway Server** section of Docker Compose Walkthrough.
- Added a note clarifying one must wait till the `full-node` has caught up with the current block number before staking their supplier.

docusaurus/docs/operate/quickstart/docker_compose_walkthrough.md

@@ -356,6 +356,8 @@ You can check that your address is funded correctly by running:
 poktrolld query bank balances $SUPPLIER_ADDR
 ```
 
+_Note: You must wait until `full-node` has synced up to the [current block #](https://shannon.testnet.pokt.network/poktroll/block) before this command and the stake command below (`poktrolld tx supplier stake-supplier...`) will work successfully. Watch your node's block height [here.](https://dev.poktroll.com/operate/quickstart/docker_compose_walkthrough#watch-the-height-)_
+
 If you're waiting to see if your transaction has been included in a block, you can run:
 
 ```bash
@@ -659,13 +661,13 @@ explains what the Gateway Server operation config is and how it can be used.
 appgate/config/gateway_config.yaml
 
 ```bash
-docker-compose up -d gateway-example
+docker-compose up -d gateway
 ```
 
 Check logs and confirm the node works as expected:
 
 ```bash
-docker-compose logs -f --tail 100 gateway-example
+docker-compose logs -f --tail 100 gateway
 ```
 
 ### Delegate your Application to the Gateway <!-- omit in toc -->