feat(examples): add hello_world, update `r/demo/event` #6297

Job	Run time
setup	5s
Run Main (gnodev) / Go Linter / lint	34s
Run Main (gnodev) / Go Build / generated	7s
Run Main (gnodev) / Go Test / test	5m 30s
Run Main (gnofaucet) / Go Build / generated	7s
Run Main (gnofaucet) / Go Test / test	24s
Run Main (gnogenesis) / Go Build / generated	11s
Run Main (gnofaucet) / Go Linter / lint	14s
Run Main (gnogenesis) / Go Linter / lint	25s
Run Main (gnogenesis) / Go Test / test	18s
Run Main (gnokeykc) / Go Build / generated	5s
Run Main (gnokeykc) / Go Test / test	15s
Run Main (gnokeykc) / Go Linter / lint	19s
Run Main (gnomd) / Go Build / generated	12s
Run Main (gnomd) / Go Linter / lint	24s
Run Main (gnomd) / Go Test / test	20s
Run Main (gnomigrate) / Go Build / generated	12s
Run Main (gnomigrate) / Go Linter / lint	31s
Run Main (gnomigrate) / Go Test / test	18s
	10m 31s

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