Improve and document release / changelog process

[sergeychernyshev]

We use changesets package to automate our release workflow and generate changelog automatically.

Commands to run are documented in .changesets/README.md

It is used in telescope and waterfall packages both of which are published to NPM and can be used in telescope-web when we are going to start publishing it to npm.

We have a few options:

1. disable automated attribution in config.json using disableThanks: true and manually add attribution
2. write our own formatter that is smarter than default @changesets/changelog-github which checks commit author only
3. configure @changesets/changelog-github to use co-contributors or other additional PR tags on the commit as authors instead of a person doing the comiting. It is either already supported and it is not as dumb as it looks, or we need to contribute this support