Add explicit dependencies required by custom Markdown utility in pola…

…ris.shopify.com

These dependencies are imported directly in our custom fork of a
markdown formatting tool but aren't added as dependencies because they
came transitively through the library before. Now they must be explicit
dependencies, because pnpm will not make them available to the top-level
otherwise

polaris.shopify.com/package.json

@@ -72,8 +72,10 @@
     "@types/lodash.mapvalues": "^4.6.9",
     "@types/lodash.throttle": "^4.1.7",
     "@types/marked": "^4.0.3",
+    "@types/mdast": "^3.0.10",
     "@types/prismjs": "^1.26.0",
     "@types/react": "^18.2.0",
+    "@types/unist": "^2.0.6",
     "@types/uuid": "^9.0.1",
     "babel-plugin-preval": "^5.1.0",
     "chalk": "^5.2.0",
@@ -99,6 +101,8 @@
     "satori": "^0.10.11",
     "style-loader": "^3.3.1",
     "ts-node": "^10.7.0",
-    "typescript": "^4.9.3"
+    "typescript": "^4.9.3",
+    "unified": "^10.1.2",
+    "unist-util-visit": "^4.1.0"
   }
 }