Make releases EZ

[insipx]

PR adds a github action workflow which automates releases. It will run whenever the branch release gets pushed to. Once it's pushed to, the workflow:

• Builds polkadot-archive in --release, packages binary in .deband also standalone linux (as with all previous releases)
• Reads from Changelog to fill in release notes in body of release, as well as assign release tag & name

This PR also fixes CHANGELOG to follow keep a changelog, and creates a separate CHANGELOG for polkadot-archive. This will make it easier to update in the future I think.

This won't publish the release, but it will create a draft that we can look over and modify and then publish from Github UI. This is my preferred way, just because it forces double-checking things, but I'm open to other opinions

I suspect this could further be automated by adding a dienerstep to automatically change all substrate/polkadot refs to the latest release with some more github-action magic.

I was testing this stuff out earlier in a personal repo before creating the action (Release branch): https://github.com/insipx/test-gh-action

[emostov]

Look good from what I understand; just a question about how the changelog reader knows how to get the version. Is there a way to test without actually merging to the release branch?

[maciejhirsz]

One minor thing found.

[niklasad1]

looks cool.