release: bump version to 0.4.0

- Documentation updates.
- `estimate-gas-execute-script` RPC command added.
- The URL option for the node command added.
- `create-tx` command implemented.
- `get-module-abi` RPC command output improved.

Cargo.toml

@@ -3,7 +3,7 @@ name = "smove"
 authors = ["Eiger <hello@eiger.co>"]
 description = "CLI frontend for the Move compiler and VM in Substrate"
 repository = "https://github.com/eigerco/smove"
-version = "0.3.0"
+version = "0.4.0"
 edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html