Fix JQuery SumoSelect Warning: constant(): Couldn't find constant CSS_PLUGINS in Library Discovery Parser

Problem/Motivation

Having the following in the vardoc_theme.library.yml file

    plugins:
      css/plugins/sumoselect.css: {}

Which is not SMACS or in the Drupal theming engine

It bringing out the following warning and not loading the library

Warning: constant(): Couldn't find constant CSS_PLUGINS in Drupal\Core\Asset\LibraryDiscoveryParser->buildByExtension() (line 165 of core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php).
Drupal\Core\Asset\LibraryDiscoveryParser->buildByExtension('vardoc_theme') (Line: 87)
Drupal\Core\Asset\LibraryDiscoveryCollector->getLibraryDefinitions('vardoc_theme') (Line: 66)
Drupal\Core\Asset\LibraryDiscoveryCollector->resolveCacheMiss('vardoc_theme') (Line: 149)
Drupal\Core\Cache\CacheCollector->get('vardoc_theme') (Line: 100)
Drupal\Core\Asset\LibraryDiscoveryCollector->getLibraryDefinitions('vartheme_bs4') (Line: 66)
Drupal\Core\Asset\LibraryDiscoveryCollector->resolveCacheMiss('vartheme_bs4') (Line: 149)
Drupal\Core\Cache\CacheCollector->get('vartheme_bs4') (Line: 100)
Drupal\Core\Asset\LibraryDiscoveryCollector->getLibraryDefinitions('bootstrap_barrio') (Line: 66)
Drupal\Core\Asset\LibraryDiscoveryCollector->resolveCacheMiss('bootstrap_barrio') (Line: 149)
Drupal\Core\Cache\CacheCollector->get('bootstrap_barrio') (Line: 149)
Drupal\Core\Asset\LibraryDiscoveryCollector->applyLibrariesExtend('core', 'drupal.dropbutton', Array) (Line: 111)
Drupal\Core\Asset\LibraryDiscoveryCollector->getLibraryDefinitions('core') (Line: 66)
Drupal\Core\Asset\LibraryDiscoveryCollector->resolveCacheMiss('core') (Line: 149)
Drupal\Core\Cache\CacheCollector->get('core') (Line: 44)
Drupal\Core\Asset\LibraryDiscovery->getLibrariesByExtension('core') (Line: 58)
Drupal\Core\Asset\LibraryDiscovery->getLibraryByName('core', 'jquery') (Line: 68)
Drupal\Core\Asset\LibraryDependencyResolver->doGetDependencies(Array, Array) (Line: 70)
Drupal\Core\Asset\LibraryDependencyResolver->doGetDependencies(Array) (Line: 41)
Drupal\Core\Asset\LibraryDependencyResolver->getLibrariesWithDependencies(Array) (Line: 104)
Drupal\Core\Asset\AssetResolver->getLibrariesToLoad(Object) (Line: 116)
Drupal\Core\Asset\AssetResolver->getCssAssets(Object, ) (Line: 315)
Drupal\Core\Render\HtmlResponseAttachmentsProcessor->processAssetLibraries(Object, Array) (Line: 161)
Drupal\Core\Render\HtmlResponseAttachmentsProcessor->processAttachments(Object) (Line: 94)
Drupal\big_pipe\Render\BigPipeResponseAttachmentsProcessor->processAttachments(Object) (Line: 45)
Drupal\Core\EventSubscriber\HtmlResponseSubscriber->onRespond(Object, 'kernel.response', Object)
call_user_func(Array, Object, 'kernel.response', Object) (Line: 142)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch(Object, 'kernel.response') (Line: 191)
Symfony\Component\HttpKernel\HttpKernel->filterResponse(Object, Object, 1) (Line: 179)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 80)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 706)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Proposed resolution

Add the jquery.sumoselect library using the right way
with Gulp + Drupal theme engine

Remaining tasks

User interface changes

• None

API changes

• None

Data model changes

• None