add html5 preset, some files structure changes

packages/bbob-core/lib/index.js

@@ -0,0 +1,20 @@
+class BBob {
+  constructor(plugins) {
+  }
+
+  parse() {
+
+  }
+
+  stringify() {
+
+  }
+
+  process(input) {
+
+  }
+}
+
+module.exports = function bbob(...plugins) {
+  return new BBob(plugins);
+};