docs: add mention of modes from 0.35 (#11167)

Author: tac0turtle

docs/run-node/run-node.md

@@ -114,9 +114,11 @@ One example config to tweak is the `minimum-gas-prices` field inside `app.toml`,
 Now that everything is set up, you can finally start your node:
 
 ```bash
-simd start
+simd start --mode validator
 ```
 
+> Note: By default nodes are run in full node mode. Running a local network means in most cases, the node is the only node in the network, requiring you to set the mode. 
+
 You should see blocks come in.
 
 The previous command allow you to run a single node. This is enough for the next section on interacting with this node, but you may wish to run multiple nodes at the same time, and see how consensus happens between them.