release v0.3.4 (#269)

doc/release-notes/rl-0.3.4.md

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+## Release 0.3.4 (2023-09-28)
+
+This release addresses several bugs and improvements, including:
+- Fixed bugs affecting `flox (activate|containerize|publish)`.
+- Fixed bug affecting output from `--verbose`.
+- Updated flox RPM and Debian installers to support single-user mode installation into containers.
+- Worked on changes in the background to the flox CLI as we aim for our general availability (1.0) release.
+
+We especially want to thank all our github.com/flox/flox contributors and discourse community members for all your valuable feedback!