Add support for PHP8

[arku31]

Close #7

I was able to execute this
/usr/local/Cellar/php/8.0.1_1/bin/php composer.phar install

and

PHPUnit 9.5.4 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.0.1
Configuration: /usr/local/Cellar/php/8.0.1_1/bin/laravel-logzio/phpunit.xml.dist
Warning:       Your XML configuration validates against a deprecated schema.
Suggestion:    Migrate your XML configuration using "--migrate-configuration"!

..............                                                    14 / 14 (100%)

Time: 00:00.117, Memory: 18.00 MB

OK (14 tests, 28 assertions)

[coveralls]

Pull Request Test Coverage Report for Build 711994512

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 710893542:	0.0%
Covered Lines:	48
Relevant Lines:	48

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💛 - Coveralls

[oanhnn]

Thankyou !