Github Action: Check unit tests

[renatonascalves]

As titled.

• Fixes for ES: 8.3.2 | PHP: 8.0 will be added in a separate pull request.
• [x] Remove support for PHP 5-7.3 (PHP 7.4+)
• [x] Remove support for ES 1.x and 2.x
• [x] Support the latest 3 ES major versions
• [x] Deprecating Travis (including the bin/ bash files)

fixes #145

[renatonascalves]

🎉 This is ready for review! 🍡