Update DEVELOPER_GUIDE.md

Author: josephrhobbs

DEVELOPER_GUIDE.md

@@ -15,13 +15,15 @@ The following instructions will guide you to adding a Carlo langauge subcommand.
 
 1. Create a Cargo library package in the `subcommands` directory with the name `sc`, where `sc` is your desired subcommand name.  The package should have name `carlo-sc`.
 
-2. Create a function in your subcommand library named `sc`.  It is recommended that you import `carlotk::prelude::*` so you can use the Carlo tokenizer, parser, and environment utilities.  Your function must have the following signature: `fn(CliArgs) -> ()`.
+2. Add `carlotk` to your subcommand library's `Cargo.toml` file.
 
-3. Create the following entry in `Cargo.toml`.
+3. Create a function in your subcommand library named `sc`.  It is recommended that you import `carlotk::prelude::*` so you can use the Carlo tokenizer, parser, and environment utilities.  Your function must have the following signature: `fn(CliArgs) -> ()`.
+
+4. Create the following entry in `Cargo.toml`.
 
 ```
 [dependencies.sc]
 path = "./subcommands/sc"
 ```
 
-4. In `src/main.rs`, add `subcommand sc` (on a new line) to the `include_subcommands!` macro invocation.
+5. In `src/main.rs`, add `subcommand sc` (on a new line) to the `include_subcommands!` macro invocation.