Add multiplayer-bomber example. #2874

Job	Run time
license-guard	33s
clippy	1m 47s
godot-itest (macos)	57s
doc-lints	42s
godot-itest (windows)	2m 16s
run-examples	1m 34s
godot-itest (linux-full)	2m 41s
rustfmt	21s
godot-itest (linux-features-experimental)	2m 5s
unit-test	2m 43s
godot-itest (linux-4.1)	1m 12s
godot-itest (linux-4.2)	1m 6s
godot-itest (linux-memcheck)	2m 33s
ci-status	2s
	20m 32s

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