Realse of v2

The main focus of the release was to add API description to servers.
The servers are augmented with info on API structure. It allows us to build OpenApi schema, swagger and clients for servers.
Main features:

• tutorial and quickstart guide on github pages
• OpenApi schema for servers
• swagger servers support
• clients from the same code as servers
• redesign of internal types
• redesign of DSL for routes
• many ergonomic improvements
• packages for extra utils
• split of mig package to several packages:
  • mig - core
  • mig-wai - rendering servers to wai apps
  • mig-client - clients
  • mig-extra - extra utils
  • mig-server - mig servers with batteries
  • mig-swagger-ui - swagger ui server
• CI for repo with formatter, build and tests and update of docs on github pages

Thanks to Ambros for contribution.