Add possibility to add strict_type or other declares on the PhpFile

[fghamsary]

Add feature to be able to add declare on PhpFile such as strict_type easily.
For the feature request: #15

[murtukov]

Hey @fghamsary, thank you for your work. Could you please resolve the conflicts?

[fghamsary]

Hello there as two years have passed, I didn't check the repository anymore. Now that I needed new Enum on PHP I came to see that you have answered :)
Two years after you answered, and two years for me to coming back to you.
I'll update my own repository for all the pull requests that I have done so that I can use the Enum as well. I was going to add this, but you already did it.
Thanks for your work.