OCaml.gitignore: Ignore binary files containing info about compilation

See https://ocaml.org/manual/comp.html#s:comp-overview.

OCaml.gitignore

@@ -8,6 +8,13 @@
 *.cmxs
 *.cmxa
 
+# Files containing detailed information about the compilation (generated
+# by `ocamlc`/`ocamlopt` when invoked using the option `-bin-annot`).
+# These files are typically useful for code inspection tools
+# (e.g. Merlin).
+*.cmt
+*.cmti
+
 # ocamlbuild and Dune default working directory
 _build/