docs(docs): restructure and expand documentation with new phases and content

docs/solutions/(two-pointers)/01-reverse-string.mdx

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+---
+title: '344. Reverse String'
+sidebar:
+  badge: 'Easy'
+---
+
+<Badge variant="accent">Two Pointers</Badge>
+<Badge>[Source](https://leetcode.com/problems/reverse-string/)</Badge>
+
+## Description

docs/solutions/(two-pointers)/02-squares-of-a-sorted-array.mdx

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+---
+sidebar:
+  icon: code
+  badge: '977'
+---