snippets: add snippets for reference comment in md

Co-Authored-by: iGor milhit <igor@milhit.ch>

my_snippets/markdown.lua

@@ -206,5 +206,21 @@ return {
         i(1, "tags")
       }
     )
+  ),
+  s(
+    {
+      trig = "refsen",
+      name = "References",
+      dscr = "Insert an HTML comment for references."
+    },
+    t("<!-- references -->")
+  ),
+  s(
+    {
+      trig = "refsfr",
+      name = "Références",
+      dscr = "Insert an HTML comment for references, but in French."
+    },
+    t("<!-- références -->")
   )
 }