[BC] Upgraded dependencies, dropped support for anything below PHP 8.0. (#849)

* GitHub actions + style fixes + updated packages

* Fixed workflows dir

* Support for PHP 8.1 (#1)

* Update README.md

* Revert some changes from upstream

tests/FFMpeg/BaseTestCase.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace Tests\FFMpeg;
+
+use PHPUnit\Framework\TestCase;
+
+class BaseTestCase extends TestCase
+{
+    public function assertScalar($value, $message = '')
+    {
+        $this->assertTrue(is_scalar($value), $message);
+    }
+}