Add multiplayer-bomber example. #2871

Job	Run time
doc-lints	49s
clippy	1m 47s
license-guard	31s
godot-itest (macos)	1m 16s
run-examples	1m 31s
godot-itest (windows)	3m 23s
unit-test	2m 37s
godot-itest (linux-full)	2m 33s
godot-itest (linux-features-experimental)	2m 1s
rustfmt	17s
godot-itest (linux-4.1)	1m 12s
godot-itest (linux-4.2)	1m 28s
godot-itest (linux-memcheck)	2m 17s
ci-status	2s
	21m 44s

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