v5.12.0 release notes

• fsutil:
  • Extended the known list of extension for fsutil.DetectContentTypeByExtension()
  • Added fsutil.AddExtensionType() that allows to add or override items in the list of known extensions.
  • Added SVG signature sniffing to the content type detection. SVG files should now be detected as image/svg+xml instead of text/xml.
• errors: minor optimization to avoid reallocations of the reasons slice.
• Bump minimum go version to 1.25.8.