Ocaml project "Implement a Language with LLVM in OCaml" is archived

[OpticFusion1]

Imported from practical-tutorials#545

Original author: @muzimuzhi
Original issue title: Ocaml project "Implement a Language with LLVM in OCaml" is archived

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LLVM removed its OCaml tutorial since v13.0.0 (see llvm/llvm-project@4fc6ff0), perhaps because it's "not updated for a long time."

• LLVM tutorial, latest version https://llvm.org/docs/tutorial
• LLVM tutorial, v12.0.1 (the last version which provides OCaml tutorial)
  https://releases.llvm.org/12.0.1/docs/tutorial/index.html
• LLVM tutorial, v13.0.0 (the first version which removed OCaml tutorial)
  https://releases.llvm.org/13.0.0/docs/tutorial/index.html