build: add the tslint gulp task (#14481)

tools/gulp-tasks/README.md

@@ -37,7 +37,7 @@ module.exports = {
 The tasks are loaded in the gulp file, by requiring them. There is a helper called `loadTask(fileName, taskName)`
 will do this for us, where the `taskName` is optional if the file only exports one task.
 
-E.g. Loading the task that will run the build, from a task file that contans only one task.
+E.g. Loading the task that will run the build, from a task file that contains only one task.
 
 ```js
 gulp.task('build.sh', loadTask('build'));