🚧 Add stream to map

Still need to handle the codecs. But almost there.

src/Stream.php

@@ -0,0 +1,76 @@
+<?php
+
+namespace Danjones\FFMpeg;
+
+use FFMpeg\Format\FormatInterface;
+
+class Stream
+{
+    use Traits\HasMetadata;
+
+    protected Map $map;
+    protected FormatInterface $codec;
+    protected string $input = '0:0';
+    protected array $flags = [];
+
+    public function __construct(Map $map)
+    {
+        $this->map = $map;
+    }
+
+    public function setInput(string $input): static
+    {
+        $this->input = $input;
+
+        return $this;
+    }
+
+    public function addFlag(string $key, string $value): static
+    {
+        $this->flags[$key] = $value;
+
+        return $this;
+    }
+
+    public function setCodec(FormatInterface $codec): static
+    {
+        $this->codec = $codec;
+
+        return $this;
+    }
+
+    protected function parseCodec(): static
+    {
+        // @todo
+        $this->addFlag('c', 'libx265');
+
+        return $this;
+    }
+
+    public function saveStream(): Map
+    {
+        $this->map->saveStream($this);
+
+        return $this->map;
+    }
+
+    public function buildCommand(int $idx = 0): array
+    {
+        $this->parseCodec();
+
+        $commands = [];
+
+        $commands[] = '-map';
+        $commands[] = $this->input;
+
+        foreach ($this->flags as $k => $v) {
+            array_push($commands, "-{$k}:{$idx}", $v);
+        }
+
+        foreach ($this->metadata as $k => $v) {
+            array_push($commands, "-metadata:s:{$idx}", "{$k}={$v}");
+        }
+
+        return $commands;
+    }
+}