add to opam file

Author: zth

tools.opam

@@ -8,6 +8,7 @@ homepage: "https://github.com/rescript-lang/rescript-compiler"
 bug-reports: "https://github.com/rescript-lang/rescript-compiler/issues"
 depends: [
   "ocaml" {>= "4.14"}
+  "cmarkit" {>= "0.3.0"}
   "cppo" {= "1.8.0"}
   "analysis"
   "dune" {>= "3.17"}