docs(generators:controller): create controller.md

[skip ci]

Author: Awk34

docs/generators/controller.md

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+### Controller
+Generates a controller.
+
+Example:
+```bash
+yo angular-fullstack:controller user
+[?] Where would you like to create this controller? client/app/
+```
+
+Produces:
+
+    client/app/user/user.controller.js
+    client/app/user/user.controller.spec.js