Switch to Blueprintjs v4

package.json

@@ -12,13 +12,14 @@
     "add-new-language": "node scripts/add-new-language.js"
   },
   "dependencies": {
-    "@blueprintjs/core": "^3.51.3",
+    "@blueprintjs/core": "^4.0.0-beta.12",
     "@monaco-editor/react": "^4.3.1",
     "monaco-editor": "^0.30.1",
     "next": "12.0.7",
     "react": "17.0.2",
     "react-dom": "17.0.2",
-    "react-mosaic-component": "^5.0.0"
+    "react-mosaic-component": "^5.0.0",
+    "sass": "^1.49.7"
   },
   "devDependencies": {
     "@types/jest": "^27.4.0",