feat(examples): add source code view doc, add `r/` README #6416

Job	Run time
setup	4s
Run Main (gnodev) / Go Linter / lint	41s
Run Main (gnodev) / Go Build / generated	11s
Run Main (gnodev) / Go Test / test	1m 1s
Run Main (gnofaucet) / Go Linter / lint	19s
Run Main (gnofaucet) / Go Build / generated	12s
Run Main (gnofaucet) / Go Test / test	27s
Run Main (gnogenesis) / Go Build / generated	11s
Run Main (gnogenesis) / Go Linter / lint	30s
Run Main (gnogenesis) / Go Test / test	28s
Run Main (gnohealth) / Go Build / generated	7s
Run Main (gnohealth) / Go Test / test	13s
Run Main (gnohealth) / Go Linter / lint	16s
Run Main (gnokeykc) / Go Build / generated	8s
Run Main (gnokeykc) / Go Linter / lint	23s
Run Main (gnokeykc) / Go Test / test	25s
Run Main (gnomd) / Go Build / generated	6s
Run Main (gnomd) / Go Linter / lint	22s
Run Main (gnomd) / Go Test / test	21s
Run Main (gnomigrate) / Go Build / generated	5s
Run Main (gnomigrate) / Go Linter / lint	32s
Run Main (gnomigrate) / Go Test / test	23s
	7m 25s

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