Release a new version of Notation Client

[iamsamirzon]

Since notation v0.7.1-alpha.1, we found many bugs and fixed them in the main branch.

It is the time to release a patched release

#119
There are lot of other updates as well.

• Decide on main commit for a release a80418b
• Cut branch named v0.9.0-alpha.1 based on agreed upon main commit
• Cut a tag named v0.9.0-alpha.1
• Update README.md

[dtzar]

I propose v0.9.0-alpha.1 as the version to match the version for notation-go notaryproject/notation-go#48

[dtzar]

Remaining PRs which are pretty much ready to go I think we should merge before cut:

• Fix pluginConfig parsing #181
• use notation-core-go crypto utils #180
  • Holding on use notation-core-go crypto utils #180, as we don't want to break the automated CI, and we're not quite ready to merge Fix package name and add DER parsing support notation-core-go#3.
• Bump github.com/urfave/cli/v2 from 2.4.8 to 2.8.1 #184
• Bump goreleaser/goreleaser-action from 2 to 3 #178
• Bump github.com/docker/cli from 20.10.14+incompatible to 20.10.16+incompatible #177

[SteveLasker]

@dtzar, would you take the honors to update the readme?

[dtzar]

Done. #187

[dtzar]

We're good to with the release!
https://github.com/notaryproject/notation/releases/tag/v0.9.0-alpha.1