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

apps/docs/content/(04-relational)/graph-bfs/127-word-ladder.mdx

@@ -1,6 +1,7 @@
 ---
 title: '127. Word Ladder'
 description: 'A transformation sequence from word beginWord to word endWord using a dictionary wordList is a sequence of words beginWord -> s1 -> s2 -> ... -> sk such that:'
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Word Ladder'
   badge: 'Hard'

apps/docs/content/(04-relational)/graph-bfs/994-rotting-oranges.mdx

@@ -1,6 +1,7 @@
 ---
 title: '994. Rotting Oranges'
 description: 'You are given an m x n grid where each cell can have one of three values:'
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Rotting Oranges'
   badge: 'Medium'