Release v0.4.0-alpha.4

This is a release note after v0.4.0-alpha.2 release.
Please refer previous release note https://github.com/foriequal0/git-trim/releases/tag/v0.4.0-alpha.2
I've missed some commits in alpha.3, so I skip it.

Breaking changes

• Merge --scan into --delete #163
  It also removed --delete all option, local non-tracking branches scanning by default.
• Don't protect local branches that just track bases's upstreams #164

Enhancements

• Print detailed messages why branches are filtered #162

https://github.com/foriequal0/git-trim/pulls?q=merged%3A2020-08-22..2020-09-08+sort%3Aupdated-desc+

https://crates.io/crates/git-trim/0.4.0-alpha.4