[WIP] Add Multiplayer Example #2850

Job	Run time
clippy	1m 42s
doc-lints	53s
godot-itest (macos)	1m 24s
godot-itest (windows)	2m 57s
license-guard	34s
run-examples	1m 20s
godot-itest (linux-full)	2m 22s
rustfmt	14s
godot-itest (linux-features-experimental)	45s
godot-itest (linux-4.1)	1m 20s
unit-test	2m 48s
godot-itest (linux-4.2)	1m 29s
godot-itest (linux-memcheck)	2m 20s
ci-status	3s
	20m 11s

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