Description
When providing paths configuration for twig templates all files in those paths are handled as templates which leads to cache:warmup crashes when paths contain non twig templates because of invalid syntax.

Example

# twig.yaml
twig:
  extensions:
    - .html.twig
    - .html

Context
I have to serve an angular app through symfony server because the source code should be protected by security firewall.
Angular project is located in separate directory.

To deploy into Symfony I:

• build angular app
• copy build output to symfony project
• have twig path configured to target build output based on environment

# twig.yaml
twig:
  paths:
    "angular/webapp/dev": "webapp"

Then in my controller I can render app template and inject configuration:

// controller pseudo code
class Controller {
  public function index() {
    return $this->render("webapp/index.html", $data);
  }
}

This worked in Symfony 4 but after upgrading to Symfony 5 i encounter template syntax error on cache:warmup and :clean because angular directory contains javascript files which are not valid twig templates.

An option to filter files by extension would solve this problem.