Add support for PHP 8

[internalsystemerror]

Q	A
Documentation	no
Bugfix	no
BC Break	no
New Feature	yes
RFC	no
QA	no

Description

Closes #6 .

[Xerkus]

Pre-release semantics is 0.<major>.<minor> iirc, should we target 0.1.6 here?

[boesing]

I'd be fine with 1.0 as well as this package didn't received any changes for almost 2 years.
Would assume its stable tho.

[Xerkus]

@internalsystemerror FYI convention is to name the file .gitkeep with the dot at the beginning, to match .gitignore. it originates from the *nix convention where files and folders starting with dot are "hidden" files.