fix(core): fix linting for Stylus partials

Linting was working only on main entry point file, other Stylus partials were completely ignored.
The solution was to create two gulp streams one for linting and one for processing. The linting
stream watches over all partials, while the process stream handles only the entry point file.

src/tasks/process.ts

@@ -107,14 +107,20 @@ async function taskFn(done: any, { logger, config, paths, env, gulp }: any = {})
   };
 
   return new Promise((resolve, reject) => {
-    // Set the source path and filter unchanged files
-    gulp.src(entryPointPath, { since: gulp.lastRun(taskFn) })
+    // Create stream for linting Stylus partials
+    gulp.src(path.join(sourceDirPath, '**/*.styl'))
       // Initialize gulp-plumber to prevent process termination in case of error
       .pipe(plumber({ errorHandler: error => logger.fatal(error.message) }))
       // Perform Stylus linting
       .pipe(stylint(configs.stylint))
       // Report Stylint errors if any
       .pipe(stylint.reporter())
+      .pipe(plumber.stop());
+
+    // Create stream for Stylus partials processing
+    gulp.src(entryPointPath, { since: gulp.lastRun(taskFn) })
+      // Initialize gulp-plumber to prevent process termination in case of error
+      .pipe(plumber({ errorHandler: error => logger.fatal(error.message) }))
       // Initialize source-maps only in development mode
       .pipe(gulpif(env === 'development', sourcemaps.init()))
       // Compile Stylus files