[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/Unit/FFProbe/DataMapping/AbstractDataTest.php

@@ -0,0 +1,52 @@
+<?php
+
+namespace Tests\FFMpeg\Unit\FFProbe\DataMapping;
+
+use FFMpeg\FFProbe\DataMapping\AbstractData;
+use Tests\FFMpeg\Unit\TestCase;
+
+class AbstractDataTest extends TestCase
+{
+    public function testHas()
+    {
+        $imp = new Implementation(['key1' => 'value1', 'key2' => 'value2']);
+
+        $this->assertTrue($imp->has('key1'));
+        $this->assertTrue($imp->has('key2'));
+        $this->assertFalse($imp->has('value1'));
+        $this->assertFalse($imp->has('key3'));
+    }
+
+    public function testGet()
+    {
+        $imp = new Implementation(['key1' => 'value1', 'key2' => 'value2']);
+
+        $this->assertEquals('value1', $imp->get('key1'));
+        $this->assertEquals('value2', $imp->get('key2'));
+    }
+
+    public function testGetDefault()
+    {
+        $imp = new Implementation(['key1' => 'value1', 'key2' => 'value2']);
+        $this->assertSame('yololo', $imp->get('key3', 'yololo'));
+    }
+
+    public function testKeys()
+    {
+        $imp = new Implementation(['key1' => 'value1', 'key2' => 'value2']);
+
+        $this->assertEquals(['key1', 'key2'], $imp->keys());
+    }
+
+    public function testAll()
+    {
+        $values = ['key1' => 'value1', 'key2' => 'value2'];
+        $imp = new Implementation($values);
+
+        $this->assertEquals($values, $imp->all());
+    }
+}
+
+class Implementation extends AbstractData
+{
+}