uploadRichPresence(appid, richPresence) {
		// Maybe someday in the future we'll have a proper binary KV encoder. For now, just do it by hand.
		let buf = new ByteBuffer(1024, ByteBuffer.LITTLE_ENDIAN);
		buf.writeByte(0);
		buf.writeCString('RP');
		for (let i in richPresence) {
			if (!Object.hasOwnProperty.call(richPresence, i)) {
				continue;
			}

			buf.writeByte(1); // type string
			buf.writeCString(i);
			buf.writeCString(richPresence[i]);
		}
		buf.writeByte(8); // end
		buf.writeByte(8); // end again

		this._send({
			// Header
			msg: EMsg.ClientRichPresenceUpload,
			proto: {routing_appid: appid}
		}, {
			// Request
			rich_presence_kv: buf.flip().toBuffer()
		});
	}
Upload some rich presence data to Steam.
@param {int} appid
@param {{steam_display?, connect?}} richPresence