Bump version to 1.0.0-alpha.2 #20

Job	Run time
plan	17s
build-local-artifacts (x86_64-unknown-linux-gnu)	5m 12s
build-local-artifacts (x86_64-pc-windows-msvc)	10m 32s
build-local-artifacts (aarch64-apple-darwin)	3m 45s
build-local-artifacts (x86_64-apple-darwin)	5m 18s
build-local-artifacts (aarch64-unknown-linux-gnu)	4m 38s
build-global-artifacts	14s
host	24s
announce	8s
	30m 28s

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