Release v0.1.0-beta4

[karencfv]

Release checklist

• [x] Make sure the VERSION and oxide/version.go files have the new version you want to release.
• [x] Make sure all examples and docs reference the new version.
• [x] Generate changelog by running make changelog and add date of the release to the title. https://github.com/oxidecomputer/oxide.go/pull/203
• [x] Release the new version by running make tag.
• [x] Bump the version in VERSION and oxide/version.go https://github.com/oxidecomputer/oxide.go/pull/204
• [x] Create a new file for the next release in .changelog/ https://github.com/oxidecomputer/oxide.go/pull/204