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

apps/docs/content/(01-linear-structures)/hash-table/1-two-sum.mdx

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 ---
 title: '1. Two Sum'
 description: You are given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Two Sum'
   badge: 'Easy'

apps/docs/content/(01-linear-structures)/hash-table/1832-check-if-the-sentence-is-pangram.mdx

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 ---
 title: '1832. Check if the Sentence Is Pangram'
 description: A pangram is a sentence where every letter of the English alphabet appears at least once
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Check if the Sentence Is Pangram'
   badge: 'Easy'

apps/docs/content/(01-linear-structures)/hash-table/217-contains-duplicate.mdx

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 ---
 title: '217. Contains Duplicate'
 description: Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Contains Duplicate'
   badge: 'Easy'

apps/docs/content/(01-linear-structures)/hash-table/242-valid-anagram.mdx

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 ---
 title: '242. Valid Anagram'
 description: Given two strings s and t, return true if t is an anagram of s, and false otherwise
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Valid Anagram'
   badge: 'Easy'

apps/docs/content/(01-linear-structures)/hash-table/347-top-k-frequent-elements.mdx

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 ---
 title: '347. Top K Frequent Elements'
 description: Given an integer array nums and an integer k, return the k most frequent elements. You may return the answer in any order
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Top K Frequent Elements'
   badge: 'Medium'

apps/docs/content/(01-linear-structures)/hash-table/387-first-unique-character-in-a-string.mdx

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 ---
 title: '387. First Unique Character in a String'
 description: Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1
+icon: line-dot-left-horizontal
 sidebar:
   label: 'First Unique Character in a String'
   badge: 'Easy'

apps/docs/content/(01-linear-structures)/hash-table/451-sort-characters-by-frequency.mdx

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 ---
 title: '451. Sort Characters By Frequency'
 description: Given a string s, sort it in decreasing order based on the frequency of the characters. The frequency of a character is the number of times it appears in the string
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Sort Characters By Frequency'
   badge: 'Medium'

apps/docs/content/(01-linear-structures)/hash-table/49-group-anagrams.mdx

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 ---
 title: '49. Group Anagrams'
 description: Given an array of strings strs, group the anagrams together. You can return the answer in any order
+icon: line-dot-left-horizontal
 sidebar:
   label: 'Group Anagrams'
   badge: 'Medium'