docs: add companies frontmatter, schema, and rendering in badges & appendix pages

apps/docs/content/(04-relational)/union-find/684_redundant-connection.mdx

@@ -8,6 +8,11 @@ topics:
   - { name: "Union-Find", slug: "union-find" }
   - { name: "Graph Theory", slug: "graph" }
 issue: "https://github.com/prdlk/leetcode/issues/146"
+companies:
+  - { name: "Box", period: "Three Months", frequency: 100 }
+  - { name: "Amazon", period: "Three Months", frequency: 21.2 }
+  - { name: "Bloomberg", period: "Six Months", frequency: 25.5 }
+  - { name: "Microsoft", period: "Six Months", frequency: 24.1 }
 sidebar:
   label: 'Redundant Connection'
   badge: 'Medium'