docs(docs): add study decks, new reference pages, and fix header image path

docs/reference/01-reverse-string.mdx

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+---
+title: '344. Reverse String'
+description: Write a function that reverses a string. The input string is given as an array of characters s
+sidebar:
+  badge: 'Easy'
+---
+
+<Badge variant="accent">Two Pointers</Badge>
+
+:::warning
+You must do this by modifying the input array in-place with O(1) extra memory.
+:::
+
+### Example 1:
+- Input: `s = ["h","e","l","l","o"]`
+- Output: `["o","l","l","e","h"]`
+
+### Example 2:
+- Input: `s = ["H","a","n","n","a","h"]`
+- Output: `["h","a","n","n","a","H"]`
+
+### Constraints:
+
+- `1 <= s.length <= 10^5`
+- `s[i]` is a printable ascii character.
+
+## Solution
+
+```js
+/**
+ * @param {character[]} s
+ * @return {void} Do not return anything, modify s in-place instead.
+ */
+
+var reverseString = function(s) {
+    let i = 0;
+    let j = s.length - 1;
+    
+    while (i < j) {
+        [s[i], s[j]] = [s[j], s[i]];
+        j--;
+        i++;
+    }   
+};
+```

docs/reference/02-squares-of-a-sorted-array.mdx

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+---
+title: '977. Squares of a Sorted Array'
+description: Given an integer array nums sorted in non-decreasing order, return an array of the squares of each number sorted in non-decreasing order
+sidebar:
+  badge: 'Easy'
+---
+
+<Badge variant="accent">Two Pointers</Badge>
+
+::::warning
+Squaring each element and sorting the new array is very trivial, could you find an O(n) solution using a different approach?
+::::
+
+### Example 1:
+- Input: `nums = [-4,-1,0,3,10]`
+- Output: `[0,1,9,16,100]`
+- Explanation: After squaring, the array becomes `[16,1,0,9,100]`. After sorting, it becomes `[0,1,9,16,100]`.
+
+### Example 2:
+- Input: `nums = [-7,-3,2,3,11]`
+- Output: `[4,9,9,49,121]`
+
+### Constraints:
+
+- `1 <= nums.length <= 10^4`
+- `-10^4 <= nums[i] <= 10^4`
+- `nums` is sorted in non-decreasing order.
+
+## Solution
+
+```js
+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+var sortedSquares = function(nums) {
+  let n = nums.length;
+  let ans = new Array(nums.length);
+  let left = 0, right = nums.length - 1;
+
+  for (let i = n -1; i >= 0; i--){
+    let square;
+    if(Math.abs(nums[left]) < Math.abs(nums[right])){
+      square = nums[right];
+      right--;
+    }else{
+      square = nums[left];
+      left++;
+    }
+    ans[i] = square*square;
+  }
+  return ans;
+};
+```