docs(content): add issue URLs to problem pages and restructure guides into appendix

apps/docs/content/(05-decision-space)/greedy/53-maximum-subarray.mdx

@@ -6,6 +6,7 @@ topics:
   - { name: "Array", slug: "array" }
   - { name: "Divide and Conquer", slug: "divide-and-conquer" }
   - { name: "Dynamic Programming", slug: "dynamic-programming" }
+issue: "https://github.com/prdlk/leetcode/issues/174"
 sidebar:
   label: 'Maximum Subarray'
   badge: 'Medium'