Add more image mimetypes to reverse proxy

Add JPEG-XL, AVIF, and WebP support to the reverse proxy. All three are
supported in WebKit browsers; the latter two are supported in Gecko and
Blink.

lib/pleroma/reverse_proxy.ex

@@ -61,11 +61,14 @@ def default_cache_control_header, do: @default_cache_control_header
 
   """
   @inline_content_types [
+    "image/avif",
     "image/gif",
     "image/jpeg",
     "image/jpg",
+    "image/jxl",
     "image/png",
     "image/svg+xml",
+    "image/webp",
     "audio/mpeg",
     "audio/mp3",
     "video/webm",