Always use content to resolve content type in resources.GetRemote

This is a security hardening measure; don't trust the URL extension or any `Content-Type`/`Content-Disposition` header on its own, always look at the file content using Go's `http.DetectContentType`.

This commit also adds ttf and otf media type definitions to Hugo.

Fixes #9302
Fixes #9301

resources/images/config.go

@@ -20,6 +20,7 @@ import (
 	"strings"
 
 	"github.com/gohugoio/hugo/helpers"
+	"github.com/gohugoio/hugo/media"
 
 	"github.com/pkg/errors"
 
@@ -45,6 +46,15 @@ var (
 		".webp": WEBP,
 	}
 
+	imageFormatsBySubType = map[string]Format{
+		media.JPEGType.SubType: JPEG,
+		media.PNGType.SubType:  PNG,
+		media.TIFFType.SubType: TIFF,
+		media.BMPType.SubType:  BMP,
+		media.GIFType.SubType:  GIF,
+		media.WEBPType.SubType: WEBP,
+	}
+
 	// Add or increment if changes to an image format's processing requires
 	// re-generation.
 	imageFormatsVersions = map[Format]int{
@@ -102,6 +112,11 @@ func ImageFormatFromExt(ext string) (Format, bool) {
 	return f, found
 }
 
+func ImageFormatFromMediaSubType(sub string) (Format, bool) {
+	f, found := imageFormatsBySubType[sub]
+	return f, found
+}
+
 const (
 	defaultJPEGQuality    = 75
 	defaultResampleFilter = "box"