pre-commit: ignore all text after scissor line in COMMIT_EDITMSG

If `git` is configured to open an editor on commit (to edit a commit
message), it adds a `git diff` below the scissor line.  Tell `typos`
to ignore everything below it.

.typos.toml

@@ -9,6 +9,9 @@ extend-ignore-re = [
     "(?s)(#|/(/|\\*)|\\.\\.)\\s*(NOQA|noqa):? spellcheck(: *|=| +)off.*?\\n\\s*(#|/(/|\\*)|\\.\\.)\\s*(NOQA|noqa):? spellcheck(: *|=| +)on"
     # NOTE Allow to mark a line to exclude from spellchecking
   , "(?Rm)^.*(#|/(/|\\*)|\\.\\.)\\s*(NOQA|noqa):? spellcheck(: *|=| +)disable-line$"
+    # NOTE Stop checking from this line to the end of file
+    # This line is a marker added by Git to the `COMMIT_EDITMSG`.
+  , "(?sm)^# ------------------------ >8 ------------------------$.*"
   ]
 locale = "en-us"
 # ATTENTION If, for any reason, you want to add the