Revert "ox-html: Use <img> tags for svgs, not <object>"

This reverts commit d96e897579.

See https://orgmode.org/list/87r0dy3u91.fsf@localhost

lisp/ox-html.el

@@ -1772,6 +1772,8 @@ SOURCE is a string specifying the location of the image.
 ATTRIBUTES is a plist, as returned by
 `org-export-read-attribute'.  INFO is a plist used as
 a communication channel."
+  (if (string= "svg" (file-name-extension source))
+      (org-html--svg-image source attributes info)
     (org-html-close-tag
      "img"
      (org-html--make-attribute-string
@@ -1783,7 +1785,30 @@ a communication channel."
 		       (org-find-text-property-in-string 'org-latex-src source))
 		    (file-name-nondirectory source)))
        attributes))
-   info))
+     info)))
+
+(defun org-html--svg-image (source attributes info)
+  "Return \"object\" embedding svg file SOURCE with given ATTRIBUTES.
+INFO is a plist used as a communication channel.
+
+The special attribute \"fallback\" can be used to specify a
+fallback image file to use if the object embedding is not
+supported.  CSS class \"org-svg\" is assigned as the class of the
+object unless a different class is specified with an attribute."
+  (let ((fallback (plist-get attributes :fallback))
+	(attrs (org-html--make-attribute-string
+		(org-combine-plists
+                 ;; Remove fallback attribute, which is not meant to
+                 ;; appear directly in the attributes string, and
+                 ;; provide a default class if none is set.
+                 '(:class "org-svg") attributes '(:fallback nil)))))
+    (format "<object type=\"image/svg+xml\" data=\"%s\" %s>\n%s</object>"
+	    source
+	    attrs
+	    (if fallback
+		(org-html-close-tag
+		 "img" (format "src=\"%s\" %s" fallback attrs) info)
+	      "Sorry, your browser does not support SVG."))))
 
 (defun org-html--textarea-block (element)
   "Transcode ELEMENT into a textarea block.