Properly handles Stimulus controller in parent folders

If you try to register Stimulus controllers from another path than
`controller/` the regex do not process it properly.

Also we do not need to add `controllers--` for controller in controller
folder. See [doc](https://stimulus.hotwired.dev/handbook/installing#controller-filenames-map-to-identifiers).

Examples with dedicated stimulus view components controllers.

``js
import { Application } from "@hotwired/stimulus"

const application = Application.start()
window.Stimulus = application

import componentControllers from '../components/**/*_controller.js';
componentControllers.forEach((controller) => {
  application.register(controller.name, controller.module.default)
});

import controllers from "./**/*_controller.js"
controllers.forEach((controller) => {
  application.register(controller.name, controller.module.default)
})
```

To try this code.
```js
const ok =[
 'controllers/release_target_controller.js',
 'controllers/toggle_controller.js',
 '../components/deploy_slack_pref_component_controller.js'
].map((module) => module
            .replace(/_controller.[j|t]s$/, "")
            .replace(/^controllers\//, "") // do not namespace controllers in controllers directory
            .replace(/\.\.\//, "") // do not use parent folder anotation for controller name
            .replace(/\//g, "--")
            .replace(/_/g, '-')
          )
console.log(ok)
// [
//   'release-target',
//   'toggle',
//   'components--deploy-slack-pref-component'
// ]
```

Fix: excid3#15

README.md

@@ -65,8 +65,29 @@ import controllers from "./**/*_controller.js"
 controllers.forEach((controller) => {
   application.register(controller.name, controller.module.default)
 })
+
+// For view components
+// import componentControllers from '../components/**/*_controller.js';
+// ...
+
 ```
 
+Controller identifiers will be the name of the file + the parent folder except in `controllers/` folder:
+
+```
+app
+├── components
+│   ├── pref_component.html.erb
+│   ├── pref_component.rb
+│   └── pref_component_controller.js // identifier 'components--deploy-pref-component'
+└── javascript
+    └── controllers
+        ├── modal_controller.js // identifier 'modal'
+        └─- admin
+            └── status_controller.js // identifier 'admin--status'
+```
+
+
 #### Import ActionCable channels:
 
 ```javascript

src/index.js

@@ -40,6 +40,8 @@ const railsPlugin = (options = { matcher: /.+\..+/ }) => ({
       const controllerNames = files
           .map((module) => module
             .replace(/_controller.[j|t]s$/, "")
+            .replace(/^controllers\//, "") // do not namespace controllers in controllers directory
+            .replace(/\.\.\//, "") // do not use parent folder anotation for controller name
             .replace(/\//g, "--")
             .replace(/_/g, '-')
           )