Update for PHP 8.0 feature set (v2)

[SpartakusMd]

Hello,

This PR reflects the changes done in #49 with some fixes and rebasing on master.

The extra changes are done and checked in a project I'm using this package in, so the functionality is proven to work.

[rsereir]

@SpartakusMd what is your composer reference for your fork ? i want to use this changes in my project too pending the merge of your pull request :)

[SpartakusMd]

Here's how you can use it:

    "require": {
        "locastic/api-platform-translation-bundle": "dev-feature/php8"
    },
    "repositories": [
        {
            "type": "vcs",
            "url": "git@github.com:SpartakusMd/Locastic-ApiPlatformTranslationBundle.git"
        }
    ]
}

[SpartakusMd]

Hey @paullla, thank you for the feedback.

As a disclaimer, this PR was authored by another person in #49 but was abandoned so I took over, meaning not all changes were done by me.

I updated the PR and replied to some comments. I preferred to keep the changes but I'm happy to revert them in case you think it will be better.

If there's anything else, please leave a comment.

[paullla]

@SpartakusMd thank you! :)