Pull out gear into separate modules

common/script/content/gear/back.js

@@ -0,0 +1,13 @@
+import {back as baseBack} from './sets/base';
+
+import {back as mysteryBack} from './sets/mystery';
+import {back as specialBack} from './sets/special';
+
+let back = {
+  base: baseBack,
+  mystery: mysteryBack,
+  special: specialBack,
+};
+
+export default back;
+