[philomena] support downloading SVG files (#5643)

test/results/derpibooru.py

@@ -55,6 +55,18 @@ __tests__ = (
     "wilson_score"    : float,
 },
 
+{
+    "#url"     : "https://derpibooru.org/images/3334658",
+    "#comment" : "svg (#5643)",
+    "#category": ("philomena", "derpibooru", "post"),
+    "#class"   : philomena.PhilomenaPostExtractor,
+    "#urls"        : "https://derpicdn.net/img/view/2024/4/1/3334658__safe_alternate+version_artist-colon-jp_derpibooru+exclusive_twilight+sparkle_alicorn_pony_amending+fences_g4_season+5_-dot-svg+available_female_grin_lo.svg",
+    "#sha1_content": "eec5adf02e2a4fe83b9211c0444d57dc03e21f50",
+
+    "extension": "svg",
+    "format"   : "svg",
+},
+
 {
     "#url"     : "https://derpibooru.org/1",
     "#category": ("philomena", "derpibooru", "post"),