Add Tags for all previous releases where possible

[ripytide]

Following from #497 I know we've now started tagging future releases. I think cargo records the current commit SHA hash in a .carge_vcs_info.json file in the published compressed crate file so it might be possible to add tags for past releases also. I can go through each past release and collect the SHA hashes if we're interested in adding them as tags.

[theotherphil]

I don’t have a good sense of how much value this would add. But it can’t hurt, so if you’re happy to collect the hashes I’m happy to create tags for them all.

[ripytide]

v0.17.0: 543ec60
v0.18.0: ae1d097
v0.19.0: 9225ee2
v0.19.1: a64f803
v0.19.2: 3612eb2
v0.20.0: 3490a2e
v0.21.0: b251829
v0.22.0: 4e6694e
v0.23.0: 6a7adf4
v0.24.0: 1c756b3
v0.25.0: 44bbf5e