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

apps/docs/content/(05-decision-space)/multi-d-grid-dp/1143-longest-common-subsequence.mdx

@@ -6,6 +6,7 @@ topics:
   - { name: "String", slug: "string" }
   - { name: "Dynamic Programming", slug: "dynamic-programming" }
   - { name: "Longest Common Subsequence", slug: "longest-common-subsequence" }
+issue: "https://github.com/prdlk/leetcode/issues/168"
 sidebar:
   label: 'Longest Common Subsequence'
   badge: 'Medium'

apps/docs/content/(05-decision-space)/multi-d-grid-dp/62-unique-paths.mdx

@@ -6,6 +6,7 @@ topics:
   - { name: "Math", slug: "math" }
   - { name: "Dynamic Programming", slug: "dynamic-programming" }
   - { name: "Combinatorics", slug: "combinatorics" }
+issue: "https://github.com/prdlk/leetcode/issues/166"
 sidebar:
   label: 'Unique Paths'
   badge: 'Medium'

apps/docs/content/(05-decision-space)/multi-d-grid-dp/64-minimum-path-sum.mdx

@@ -6,6 +6,7 @@ topics:
   - { name: "Array", slug: "array" }
   - { name: "Dynamic Programming", slug: "dynamic-programming" }
   - { name: "Matrix", slug: "matrix" }
+issue: "https://github.com/prdlk/leetcode/issues/167"
 sidebar:
   label: 'Minimum Path Sum'
   badge: 'Medium'