"use strict";

var gulp = require("gulp"),
    ...
    sass = require("gulp-sass"), // Add
    bundleconfig = require("./bundleconfig.json"); // make sure bundleconfig.json doesn't contain any comments

...

// Add
gulp.task('sass', function () {
    gulp.src("./wwwroot/css/**/*.scss")
        .pipe(sass().on('error', sass.logError))
        .pipe(gulp.dest("./wwwroot/css"));
});

gulp.task("watch", function () {

    gulp.watch("./wwwroot/css/**/*.scss", ["sass"]); // Add

    getBundles(".js").forEach(function (bundle) {
        gulp.watch(bundle.inputFiles, ["min:js"]);
    });
  ...

});

...