Merge rust-bitcoin/rust-bitcoin#789: Release v0.28 RC1

1b2dbd7 0.28.0-rc.1 release (Dr Maxim Orlovsky)

Pull request description:

  We still have quite a few issues and PRs pending to be addressed/merged before full 0.28 release: see https://github.com/rust-bitcoin/rust-bitcoin/milestone/10

  Most important, we have to find a way to address #777; additionally it will be desirable to get #587, #786, #776.

  We also have quite of work to write CHANGELOG in #785

  Nevertheless I propose to start with a `beta-1` subrelease to unlock ability for `miniscript` release and downstream testing. The Taproot API looks final, and the pending PRs are addresses internal issues/bugs which is perfectly fine for beta releases.

ACKs for top commit:
  Kixunil:
    ACK 1b2dbd7

Tree-SHA512: a7bd6dd3e7a489f7fd758fb0d7a60103bfe0cdf88997b2163f163841fa1c12e7b31fa8f03b9f817a671379578dbc10a2ca583f49b64d2d2de4a9ebb57b2b9bd5

Author: apoelstra

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bitcoin"
-version = "0.27.0"
+version = "0.28.0-rc.1"
 authors = ["Andrew Poelstra <[email protected]>"]
 license = "CC0-1.0"
 homepage = "https://github.com/rust-bitcoin/rust-bitcoin/"