Replace node-sass with dart sass and fix deprecation warning

docs/package.json

@@ -44,7 +44,7 @@
     "@babel/preset-env": "^7.14.5",
     "@babel/preset-react": "^7.14.5",
     "html-loader": "^1.3.2",
-    "node-sass": "^5.0.0",
+    "sass": "^1.35.2",
     "sass-loader": "^10.1.1",
     "style-resources-loader": "^1.4.1",
     "ts-loader": "^8.1.0"

docs/src/demos/Experiments/Embeds/index.vue

@@ -54,6 +54,7 @@ export default {
 </script>
 
 <style lang="scss" scoped>
+@use "sass:math";
 ::v-deep {
   .ProseMirror {
     > * + * {
@@ -63,7 +64,7 @@ export default {
 
   .iframe-wrapper {
     position: relative;
-    padding-bottom: 100/16*9%;
+    padding-bottom: math.div(100,16)*9%;
     height: 0;
     overflow: hidden;
     width: 100%;