Bump version number to v0.7.0 #660

Job	Run time
fmt	16s
clippy-pedantic (tzdb)	12s
clippy-pedantic (tzdb_data)	8s
audit	19s
cross-miri (aarch64-unknown-linux-gnu)	38s
DevSkim	29s
cross-miri (i586-unknown-linux-gnu)	40s
doc	15s
feature-powerset	19s
cross-miri (powerpc-unknown-linux-gnu)	40s
lint (1.81)	24s
cross-miri (powerpc64-unknown-linux-gnu)	37s
Miri	51s
test	27s
lint (1.81, -Zminimal-versions)	20s
cross-miri (powerpc64le-unknown-linux-gnu)	44s
typos	5s
lint (stable)	9s
lint (stable, -Zminimal-versions)	1m 9s
lint (nightly)	23s
lint (nightly, -Zminimal-versions)	24s
	9m 29s

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