Further PHP 8 support

Merge pull request #6 from CoverGenius/php8-compat-typing

Add bool type in filter function for php 8 compat

PHP 8.1 compatibility

PRs in this release:

• #4
• #5

Appconnect time parsing & multiple headers

Adds fix for curl appconnect time parsing
Adds fix for multiple of the same header reading

Adding support for Symfony 6

Adds suppot for symfony 6

Is a fork from official, and change of namespace as the upstream is no longer supported.