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

apps/docs/content/(04-relational)/graph-dfs/133-clone-graph.mdx

@@ -1,6 +1,7 @@
 ---
 title: '133. Clone Graph'
 description: Given a reference of a node in a connected undirected graph
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Clone Graph'
   badge: 'Medium'

apps/docs/content/(04-relational)/graph-dfs/200-number-of-islands.mdx

@@ -1,6 +1,7 @@
 ---
 title: '200. Number of Islands'
 description: Given an m x n 2D binary grid grid which represents a map of '1's (land) and '0's (water), return the number of islands
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Number of Islands'
   badge: 'Medium'

apps/docs/content/(04-relational)/graph-dfs/417-pacific-atlantic-water-flow.mdx

@@ -1,6 +1,7 @@
 ---
 title: '417. Pacific Atlantic Water Flow'
 description: There is an m x n rectangular island that borders both the Pacific Ocean and Atlantic Ocean. The Pacific Ocean touches the island's left and top edges, and the Atlantic Ocean touches the island's right and bottom edges
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Pacific Atlantic Water Flow'
   badge: 'Medium'