update release-notes for new version

docs/release-notes.md

@@ -3,6 +3,43 @@ nav_order: 9
 ---
 
 # Release notes
+## Butane 0.15.0 (2022-06-21)
+
+### Features
+
+- Add arm64 support for butane container
+- Add Flatcar support
+- Stabilize OpenShift spec 4.10
+- Add GRUB password support
+- Add TranslationSet.Map() to the Go API
+- Add AddFromCommonObject() to the Go API
+
+### Bug fixes
+
+- Fix build on Windows
+- Fix Windows path handling
+
+### Misc. changes
+
+- Improve cross-platform consistency 
+- Update Dockerfile.validate to install less dependencies
+- Add error for Clevis support
+- Correctly abort on a failed specfile fetch during `make`
+- Switch to full base image for script support in container
+- Error when using setuid/setgid/sticky mode bits (MCO 4.10+) 
+- Update to ignition v2.14.0
+
+### Docs changes
+
+- Improve release-checklist
+- Update docs/examples.md to use containerized mkpasswd
+- Reordered OpenShift and RHCOS
+- Clarify setuid/setgid/sticky mode bits support
+- Clarify ARN support
+- Clarify URL schemes (MCO 4.10 && experimental)
+- Clarify compression fields (MCO 4.8 - 4.9)
+- Refactor NEWS to Markdown and move to docs site
+
 
 ## Butane 0.14.0 (2022-01-27)