0.5.0-alpha

add support of php8.0 (#76)

* update xparse libs

* fix roave/security-advisories main branch name

* up to php7.3

* update php versions in actions config

* code grooming

* code grooming

* code grooming

* change xparse libraries constraints

* remove composer.lock

* up phpunit version

* remove exception from phpDoc

* return minimum-stability definition

* remove exception annotations from tests

* announce changes

Co-authored-by: Andrei Semianovych <andrei.semianovych@linemedia.com>