backstage release v0.59.0

In this release:

• developer portal roadmap link was added to home page;
• configurable Slack support channel link was added to home page;
• “loading” and “error” states were added to the OrganizationPicker and ReleasePicker scaffolder fields;
• region and pipeline information was added to the Installations picker;
• ability to use current user name in the TemplateStringInput scaffolder field was added. See ./docs/releases/v0.59.0-changelog.md for more information.