v0.19.0

Changes

• Drop support of Python 3.7 and update CI (#578)
  (by @fantix in ee5ad26 for #578)

Fixes

• Restore uvloop.new_event_loop and other missing uvloop members to typing (#573)
  (by @graingert in 5c500ee for #573)

• Fix docstring of loop.shutdown_default_executor (#535)
  (by @Gelbpunkt in 919da56 for #535)

• Fix CI status badge (#522)
  (by @shuuji3 in 0e9ff6c for #522)