Update build.mdx

src/content/docs/v4/cli/build.mdx

@@ -12,12 +12,14 @@ Options:
   -f --format [fmt]        The module system of your application. `cjs` or `esm` (default: "esm")
   -m --mode [mode]         the mode for sern to build in. `production` or `development` (default: "development")
   -w --watch
+  --watch-command [cmd]    the command for sern to watch. if watch is not enabled, an error is thrown (default: "")
   -W --suppress-warnings   suppress experimental warning
   -p --project [filePath]  build with the provided sern.build file
   -e --env                 path to .env file
   --source-maps            Whether to add source-maps to configuration (default: false)
   --tsconfig [filePath]    Use this tsconfig
   -h, --help               display help for command
+
 ```
 
 ## Guiding Principles
@@ -105,6 +107,16 @@ type BuildOptions = {
    * default to .env.
    */
   env?: string;
+
+  // options for watch
+  watch?: {
+        /**
+         * command to run.
+         * defaults to your package
+         * manager's start command.
+         */
+        command?: string;
+  }
 };
 ```
 
@@ -135,11 +147,17 @@ the watch flag needs a `start` command. Depending on the **lock file** in your p
   if (pathExistsSync('bun.lock')) return 'bun start';
 ```
 
+
 :::tip
-supply a custom watch command with the watchCommand option. If you want sern build to only watch the build process, and not rerunning your bot,
-watchCommand should be set **exactly** to `''`
+supply a custom watch command with the watch.command option. If you want sern build to only watch the build process, and not rerunning your bot,
+watchCommand should be set **exactly** to `''` (an empty string)
 :::
 
+:::tip
+The supplied watch command is [debounced](https://www.geeksforgeeks.org/debouncing-in-javascript/) to 1.5 seconds.
+:::
+
+
 import VideoUrl from "~/assets/docs/watch-example2.mp4"
 
 <video width="640" height="360" controls type="video/mp4">