Add initial variables output

docs/scripts/read-derived-variables.js

@@ -0,0 +1,23 @@
+module.exports = plugin;
+
+var utils = require('./utils');
+
+function plugin() {
+  return (files, metalsmith, done) => {
+    setImmediate(done);
+
+    Object.keys(files).forEach(file_path => {
+      const {file_name, lines} = utils.getLines(files, file_path);
+
+      lines.forEach(line => {
+        const variable = utils.parseLine(line);
+
+        if (variable != false) {
+          console.log('variable', variable);
+        }
+      });
+
+      metalsmith.variables = variables;
+    });
+  };
+}