docs: add debug command description (#800)

Co-authored-by: Steven <[email protected]>

Author: fireairforce

readme.md

@@ -73,6 +73,7 @@ Outputs the Node.js compact build of `input.js` into `dist/index.js`.
   --stats-out [file]       Emit webpack stats as json to the specified output file
   --target [es]            ECMAScript target to use for output (default: es2015)
                            Learn more: https://webpack.js.org/configuration/target
+  -d, --debug              Show debug logs
 ```
 
 ### Execution Testing

src/cli.js

@@ -38,6 +38,7 @@ Options:
   --stats-out [file]       Emit webpack stats as json to the specified output file
   --target [es]            ECMAScript target to use for output (default: es2015)
                            Learn more: https://webpack.js.org/configuration/target
+  -d, --debug              Show debug logs
 `;
 
 // support an API mode for CLI testing