added welcome email after subscription #504

Job	Run time
vars	1s
sites / Deploy sites	7m 16s
docker / docker	5m 14s
tests / api-e2e-test	4m 45s
electron / electron (macos-latest)	8m 1s
tests / test (macos-latest)	14m 19s
electron / electron (ubuntu-latest)	26m 17s
tests / e2e-test (macos-latest)	11m 6s
tests / test (ubuntu-latest)	12m 44s
electron / electron (windows-latest)	22m 9s
tests / e2e-test (ubuntu-latest)	5m 20s
	1h 57m 12s

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