Add GHA CI workflow

[internalsystemerror]

This PR adds GitHub Actions for this repository as per https://gist.github.com/weierophinney/b003e50c3c2667d08076caf31ebd36a4.

The following actions were performed:

remove changelog
add github workflow file
remove travis workflow
remove composer.lock from gitignore
remove travis from gitattributes
add composer.lock file updated on PHP 7.4
exclude locked runs for PHP <7.3

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

[boesing]

@internalsystemerror Could you please fix the DCO as detailed here?
https://github.com/laminas/laminas-permissions-rbac/pull/18/checks?check_run_id=2280478933

Thanks in advance.

[internalsystemerror]

@boesing, sorry thought I already did. Done now

[boesing]

LGTM

One thing: Could you drop support for PHP prior 7.3?
Laminas is okay with dropping PHP support in minor versions.
There is one thing we do want to ensure:

If a PHP version is supported by this package and by https://www.php.net/supported-versions.php, we have to keep it supported.

Thats why we do not drop support for PHP 7.3 until 6 Dec 2021.

[boesing]

I'd prefer having support for PHP 7.1 just dropped here.
We can have ^7.3 in composer.json to avoid this whole file.

The composer.lock then should be created with PHP 7.3.

[boesing]

Thanks, @internalsystemerror