docs: add sidebar labels and reorganize solution docs into category folders

docs/solutions/(array)/1636-sort-array-by-increasing-frequency.mdx

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+---
+title: '1636. Sort Array by Increasing Frequency'
+description: Given an array of integers nums, sort the array in increasing order based on the frequency of the values. If multiple values have the same frequency, sort them in decreasing order
+sidebar:
+  label: 'Sort Array by Increasing Frequency'
+  badge: 'Easy'
+---
+
+<Badge variant="accent">Array</Badge>
+
+### Example 1:
+- Input: `nums = [1,1,2,2,2,3]`
+- Output: `[3,1,1,2,2,2]`
+- Explanation: `'3'` has a frequency of `1`, `'1'` has a frequency of `2`, and `'2'` has a frequency of `3`.
+
+### Example 2:
+- Input: `nums = [2,3,1,3,2]`
+- Output: `[1,3,3,2,2]`
+- Explanation: `'2'` and `'3'` both have a frequency of `2`, so they are sorted in decreasing order.
+
+### Example 3:
+- Input: `nums = [-1,1,-6,4,5,-6,1,4,1]`
+- Output: `[5,-1,4,4,-6,-6,1,1,1]`
+
+### Constraints:
+
+- `1 <= nums.length <= 100`
+- `-100 <= nums[i] <= 100`
+
+## Solution
+
+```js
+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+var frequencySort = function (nums) {
+  const freq = {};
+  for (let n of nums) freq[n] = (freq[n] || 0) + 1;
+  return nums.sort((a, b) => freq[a] - freq[b] || b - a);
+};
+```