docs(docs): add documentation for Next Greater Element I and Remove Duplicates from Sorted Array II, update redirects

apps/docs/redirects.ts

@@ -30,6 +30,7 @@ export default [
   { from: "/73", to: "/matrix-index-math/set-matrix-zeroes" },
   { from: "/74", to: "/binary-search/search-a-2d-matrix" },
   { from: "/78", to: "/backtracking/subsets" },
+  { from: "/80", to: "/two-pointers/remove-duplicates-from-sorted-array-ii" },
   { from: "/84", to: "/monotonic-stack/largest-rectangle-in-histogram" },
   { from: "/98", to: "/binary-search-tree/validate-binary-search-tree" },
   { from: "/102", to: "/tree-bfs/binary-tree-level-order-traversal" },
@@ -78,6 +79,7 @@ export default [
   { from: "/424", to: "/sliding-window/longest-repeating-character-replacement" },
   { from: "/435", to: "/intervals/non-overlapping-intervals" },
   { from: "/451", to: "/hash-table/sort-characters-by-frequency" },
+  { from: "/496", to: "/monotonic-stack/next-greater-element-i" },
   { from: "/525", to: "/prefix-sum/contiguous-array" },
   { from: "/560", to: "/prefix-sum/subarray-sum-equals-k" },
   { from: "/567", to: "/sliding-window/permutation-in-string" },