docs(content): add Merge Intervals page, quicksort guide, and bump guide badges

apps/docs/content/guides/(1-data-structures)/array.mdx

@@ -3,7 +3,7 @@ title: "Array"
 list: "https://leetcode.com/problem-list/array/"
 icon: list-ordered
 sidebar:
-  badge: '39'
+  badge: '40'
 ---
 
 :::note

apps/docs/content/guides/(2-algorithms)/sorting.mdx

@@ -3,7 +3,7 @@ title: "Sorting"
 list: "https://leetcode.com/problem-list/sorting/"
 icon: arrow-down-wide-narrow
 sidebar:
-  badge: '10'
+  badge: '11'
 ---
 
 :::note

apps/docs/content/guides/quicksort.mdx

@@ -0,0 +1,10 @@
+---
+title: "Quicksort"
+list: "https://leetcode.com/problem-list/quicksort/"
+sidebar:
+  badge: '1'
+---
+
+:::note
+This guide has not been written yet. The LeetCode list above has every problem tagged Quicksort.
+:::