…te directly via route (dayallnash)

This PR was merged into the 5.4 branch.

Discussion
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Support `statusCode` default param when loading template directly via route

_This is my first PR to Symfony, so please be patient as I get to grips with the 'admin' process of getting everything exactly how you want it!_

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       |
| License       | MIT
| Doc PR        | symfony/symfony-docs#15376

### TODO

- [x] submit changes to the documentation and update this PR with a link

### Summary

Added support for `statusCode` default parameter when loading a template directly from route via the `Symfony\Bundle\FrameworkBundle\Controller\TemplateController` controller (like [this](https://symfony.com/doc/current/templates.html#templates-render-from-route)). This will continue to default to a 200 code, but can be changed by updating your route - for instance something like this:

```
test_route:
  path: /test_route
  controller:    Symfony\Bundle\FrameworkBundle\Controller\TemplateController
  defaults:
    # the path of the template to render
    template:  'test.html.twig'
    # the status code to include in the response headers
    statusCode: 201
```
This could be useful for when you want to render a template without adding any extra business logic in a controller, but don't want to return a 200 response.

Commits
-------

5a7b666 Added support for `statusCode` default parameter when loading a template directly from route using the `Symfony\Bundle\FrameworkBundle\Controller\TemplateController` controller.