Release v0.4.0-alpha

What's Changed

• fix: fix action shell script by @hizumiaoba in #72
• Bump com.google.guava:guava from 33.2.0-jre to 33.2.1-jre by @dependabot in #74
• feat: add backup list feature by @hizumiaoba in #48
• Bump org.kohsuke:github-api from 1.321 to 1.322 by @dependabot in #79
• Add snapshot Action by @hizumiaoba in #80
• Set Window modality for disabling parent window operation by @hizumiaoba in #81
• Disable buttons in Backup Controller Manager UI for adjustment by @hizumiaoba in #78

Full Changelog: v0.3.1-alpha...v0.4.0-alpha