PHP 8 support for 2.* and 3.* versions

[xtochko]

Could you change composer restrictions from in v.2.0.4 and higher from php: ^7.1.3, php: ^7.2.5 to something like php: ^7.1.3 | ~8.0, php: ^7.2.5 | ~8.0 or >=7.1.3, >=7.2.5 to enable use it with PHP 8? Can cause some problems as it not set at a moment?