docs(docs): add page icon frontmatter to problem pages

apps/docs/content/(04-relational)/union-find/323-number-of-connected-components-in-an-undirected-graph.mdx

@@ -1,6 +1,7 @@
 ---
 title: '323. Number of Connected Components in an Undirected Graph'
 description: You have a graph of n nodes. You are given an integer n and an array edges where edges[i] = [ai, bi] indicates that there is an edge between ai and bi in the graph
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Number of Connected Components in an Undirected Graph'
   badge: 'Medium'

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

@@ -1,6 +1,7 @@
 ---
 title: '684. Redundant Connection'
 description: In this problem, a tree is an undirected graph that is connected and has no cycles
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Redundant Connection'
   badge: 'Medium'