Changelog for ki-0.3.0

[0.3.0] - Unreleased

Breaking: Remove Context type, Ki.Implicit module, and the ability to soft-cancel a Scope.
Breaking: Remove Duration type and its associated API, including waitFor and awaitFor.
Breaking: Remove Ki.Internal module.
Breaking: Generalize async to forktry.
Breaking: Generalize forkWithUnmask to forkWith.
Breaking: Make fork_ take an IO Void rather than an IO ().
Breaking: Make fork create an unmasked thread, rather than inherit the parent's masking state.
Breaking: Rename waitSTM to wait (replacing the old wait in IO).
Change: Make scoped kill threads in the order they were created.
Bugfix: Fix small memory leak related to closing a scope.
Bugfix: Fix subtle bug related to GHC's treatment of deadlocked threads.
Bugfix: make async (now forktry) propagate async exceptions.
Bugfix: make scoped safe to run with asynchronous exceptions masked.
Bugfix: propagate exceptions to creator of scope, not creator of thread
Performance: Use atomic fetch-and-add rather than a TVar to track internal child thread ids.

Misc: Replace AtomicCounter with Int to drop the atomic-primops dependency.
Bounds: Lower cabal-version from 3.0 to 2.2 because stack cannot parse 3.0.