fix: include platform in user agent #3950

Job	Run time
Build	2m 49s
Test example js-libp2p-example-browser-pubsub	2m 51s
Test example js-libp2p-example-chat	1m 28s
Test example js-libp2p-example-circuit-relay	1m 21s
Test example js-libp2p-example-connection-encryption	1m 7s
Test example js-libp2p-example-custom-protocols	1m 20s
Test example js-libp2p-example-delegated-routing	2m 11s
Test example js-libp2p-example-discovery-mechanisms	1m 37s
Test example js-libp2p-example-peer-and-content-routing	1m 48s
Test example js-libp2p-example-pnet	1m 3s
Test example js-libp2p-example-protocol-and-stream-muxing	1m 8s
Test example js-libp2p-example-pubsub	1m 46s
Test example js-libp2p-example-transports	1m 13s
Test example js-libp2p-example-webrtc-private-to-private	1m 54s
	23m 36s

Provide feedback