✨ feat: Host a relay on Hetzner (#114)

We are hosting a [MoQ](https://quic.video) relay on a remote (bare
metal) server on Hetzner

With a lot of help from @victorpahuus

packages/moq/media/mp4/index.ts

@@ -0,0 +1,37 @@
+// Rename some stuff so it's on brand.
+// We need a separate file so this file can use the rename too.
+import * as MP4 from "./rename"
+export * from "./rename"
+
+export * from "./parser"
+
+export function isAudioTrack(track: MP4.Track): track is MP4.AudioTrack {
+	// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+	return (track as MP4.AudioTrack).audio !== undefined
+}
+
+export function isVideoTrack(track: MP4.Track): track is MP4.VideoTrack {
+	// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+	return (track as MP4.VideoTrack).video !== undefined
+}
+
+// TODO contribute to mp4box
+MP4.BoxParser.dOpsBox.prototype.write = function (stream: MP4.Stream) {
+	this.size = this.ChannelMappingFamily === 0 ? 11 : 13 + this.ChannelMapping!.length
+	this.writeHeader(stream)
+
+	stream.writeUint8(this.Version)
+	stream.writeUint8(this.OutputChannelCount)
+	stream.writeUint16(this.PreSkip)
+	stream.writeUint32(this.InputSampleRate)
+	stream.writeInt16(this.OutputGain)
+	stream.writeUint8(this.ChannelMappingFamily)
+
+	if (this.ChannelMappingFamily !== 0) {
+		stream.writeUint8(this.StreamCount!)
+		stream.writeUint8(this.CoupledCount!)
+		for (const mapping of this.ChannelMapping!) {
+			stream.writeUint8(mapping)
+		}
+	}
+}