release: release version 0.4.0

This release is mostly about the fix for jj-vcs#177, which looks pretty bad
even though I think it is actually harmless. It also has `jj log -p`
contributed by @yuja!

release: bump version to 0.3.3 (skipping 0.3.2)

I forgot to bump the version to 0.3.2 before tagging and releasing it,
so the released 0.3.2 has version number 0.3.1 in the source code and
(therefore) reported from `jj --version`. I'm therefore bumping it
from 0.3.1 to 0.3.3 now, so there can be a matching 0.3.3 release.

github: new attempt at setting up automated release builds (jj-vcs#73)

My attempt at using rust-build/rust-build.action for release builds
(from bf21e65) initially seemed promising. However, the produced
musl binary build segfaulted on my Debian machine. I don't know about
the Mac and Windows binaries. I then tried switching to building with
a vendored OpenSSL (cac93e2), but then the build started failing
(https://github.com/martinvonz/jj/actions/runs/1978730621). I couldn't
figure out why it failed, so I decided to do the build in a more
manual way (without rust-build/rust-build.action), based on
https://github.com/gitext-rs/git-stack/blob/main/.github/workflows/post-release.yml
(thanks to @epage for the example and to @arxanas for the link). I
could simplify it a bit because I'm currently doing the releases via
the GitHub UI (epage's original triggers the release when a tag has
been pushed, IIUC). Let's hope that it works this time.

release: update release notes for 0.3.1

I forgot to do this when I bumped the version number.

release: bump version to 0.3.0

There's been *a lot* of changes since 0.2.0 almost a year ago. With
the attention the project has gotten recently, I feel like I should
cut a new release and start keeping a changelog. So let's start by
bumping the version to 0.3.0.