Add a rule for skipping 'doctest -m esm' on Node <9

Co-Authored-By: David Chambers <dc@davidchambers.me>

Author: Avaq

bin/doctest

@@ -16,6 +16,11 @@ opening="$(get opening-delimiter)"
 closing="$(get closing-delimiter)"
 module="$(get module-type)"
 
+if [[ "$module" == esm ]] && [[ "$(node_major_version)" -lt 9 ]] ; then
+  echo 'Skipping ESM doctests on Node.js version less than v9.0.0' >&2
+  exit 0
+fi
+
 node_modules/.bin/doctest \
   --module "$module" \
   --prefix "$prefix" \

functions

@@ -72,3 +72,7 @@ pass() {
 fail() {
   echo $'\x1B[0;31m\xE2\x9C\x98\x1B[0m' "$@"
 }
+
+node_major_version() {
+  node --print process.versions.node | cut -d . -f 1
+}