fix: add PHP license header under the PHP tag

[CommandMaker]

Hello, I discovered your plugin not long ago and loved it, I wanted to be able to put licence headers for a long time.
But I found a problem : if I use the AddLicenseGPL3 (it should do it with others too) the header would be placed before the <?php tag, causing a syntax problem. I did some kind of dirty fix so I don't know if you'll accept it but it's sufficient for me at least 😆.

Have a nice day !

[attilarepka]

Hi!
You’re right about PHP, placing the header before the <?php tag breaks things.

That said, this isn’t just a PHP-specific issue. It opens up a broader problem around how headers should be inserted depending on file context (PHP blocks, shebangs, template files, etc.). Because of that, I’d rather handle it with a more general solution instead of merging a language-specific workaround.

I’ll revisit this with a proper refactor when I have some time.

In the meantime, feel free to keep using your fork/workaround.