add initial marp implementation with sample content and build configuration

node_modules/semver/ranges/valid.js

@@ -0,0 +1,13 @@
+'use strict'
+
+const Range = require('../classes/range')
+const validRange = (range, options) => {
+  try {
+    // Return '*' instead of '' so that truthiness works.
+    // This will throw if it's invalid anyway
+    return new Range(range, options).range || '*'
+  } catch (er) {
+    return null
+  }
+}
+module.exports = validRange