format flag suggestion message

Signed-off-by: Samson Olawoyin <olawoyin.samson@outlook.com>

src/index.ts

@@ -25,14 +25,14 @@ export const run = async () => {
         native: 'app'
       }
     });
-
+    
     //Check the passed flags when installing Nightwatch and then suggest when undefined flag is been found.
     if (argv[0] !== undefined) {
       if ((argv[0] !== '--mobile') && (String(argv[0]) !== '--generate-config')) {
         const nightwatchFlags = ['--mobile', '--generate-config'];
         const checkFlags = didYouMean(argv[0], nightwatchFlags);
-
-        Logger.error(colors.red(`Did you mean flag ${checkFlags['winner']}`));
+        const msg = colors.red(`Flag ${argv[0]} is not a valid flag, did you mean`) + colors.green(` flag ${checkFlags['winner']}`);
+        Logger.error(msg);
 
         // terminate Nightwatch setup since flag does not have definition
         process.exit(0);