Fix dependency problems with bootstrap-sass by using newer sass

SassError: Invalid CSS after "...point-max: math": expected expression (e.g. 1px, bold), was ".div($grid-float-br"
  from line 12 of app/styles/styles.scss
  >> $grid-float-breakpoint-max: math.div($grid-float-breakpoint - 1) !default;

     --------------------------------^

> This error appears to be due to the use of SassC instead of dart-sass.
> SassC wraps libsass, which does not support the math.div syntax. SassC
> and libsass are deprecated.
>
> I recommend you upgrade your sass compiler to an appropriate version.
>
> -- @AprilArcus, twbs/bootstrap-sass#1224 (comment)

package.json

@@ -39,6 +39,7 @@
     "mini-css-extract-plugin": "^1.6",
     "node-sass": "^6.0.0",
     "null-loader": "^0.1.1",
+    "sass": "^1.33",
     "sass-loader": "^10.2",
     "serve-static": "^1.14",
     "style-loader": "^0.23",