0.56.0-alpha1

• customizable icons #487
• folder menu: "folder size" #535
• admin/options: new "Outbound proxy" #812
• admin/accounts: new "Allowed network address" #864
• admin: syntax highlight for html, css, js, yaml
• env DISABLE_UPDATE (for containers)
• plugins: api.setError
• other minor improvements

Full Changelog: v0.55.3...v0.56.0-alpha1