add initial marp implementation with sample content and build configuration

node_modules/mdurl/lib/format.mjs

@@ -0,0 +1,21 @@
+export default function format (url) {
+  let result = ''
+
+  result += url.protocol || ''
+  result += url.slashes ? '//' : ''
+  result += url.auth ? url.auth + '@' : ''
+
+  if (url.hostname && url.hostname.indexOf(':') !== -1) {
+    // ipv6 address
+    result += '[' + url.hostname + ']'
+  } else {
+    result += url.hostname || ''
+  }
+
+  result += url.port ? ':' + url.port : ''
+  result += url.pathname || ''
+  result += url.search || ''
+  result += url.hash || ''
+
+  return result
+};