WIP: WIP: apply bootstrap theme

* shortcuts

resource/styles/scss/crowi.scss

@@ -421,6 +421,11 @@ input.searching {
     border: 0;
   }
 }
+*/
+
+/*
+ * Helper Classes
+ */
 
 .cmd-key.mac {
   &:after {
@@ -432,4 +437,3 @@ input.searching {
     content: 'Ctrl';
   }
 }
-*/

resource/styles/scss/vendor.scss

@@ -2,5 +2,8 @@
 $bootstrap-sass-asset-helper: true;
 @import "~bootstrap-sass/assets/stylesheets/bootstrap";
 
+// import bootstrap4 utility classes
+@import "../bootstrap4/utilities";
+
 // import toastr styles
 @import '~toastr/build/toastr';