This PR was merged into the 4.2-dev branch.Discussion----------YamlEncoder handle yml format| Q             | A| ------------- | ---| Branch?       | ?| Bug fix?      | no| New feature?  | yes| BC breaks?    | no| Deprecations? | no| Tests pass?   | yes| Fixed tickets |#28768| License       | MIT`Symfony\Component\Serializer\Encoder\YamlEncoder` now handle the `yml` format too```use Symfony\Component\Serializer\Serializer;use Symfony\Component\Serializer\Encoder\YamlEncoder;$serializer = new Serializer([], [new YamlEncoder()]);$content = file_get_contents(__DIR__ . '/test.yml');$data = $serializer->decode($content, YamlEncoder::ALTERNATIVE_FORMAT);```Let me know if something is wrong for youCommits-------d8640f9 YamlEncoder handle yml extension

…nt from 'YamlEncoder' (kevin-biig)This PR was merged into the 4.2-dev branch.Discussion----------'yml' is not a format and shouldn't be visible as constant from 'YamlEncoder'A little fix of my [previous PR](#28815)This PR changes the constant visibility of the `yml` format as private.Because as@stof [mentionned](#28815 (comment)) `yml` isn't a format, so the constant  shoudn't be public.Otherwise, this will be confusing while using autocomplete, you see two formats. The user can ask himself if there is a difference between `yaml` / `yml`.No need of that :)| Q             | A| ------------- | ---| Branch?       | master| Bug fix?      | no| New feature?  | no| BC breaks?    | no| Deprecations? | no| Fixed tickets | -| License       | MIT| Doc PR        |Commits-------674b359 'yml' is not a format and shouldn't be visible as constant from 'YamlEncoder' class