LibWeb: Parse src: local(...) in CSS @font-face rules

Note that we don't load the local font as specified, but at least we no
longer reject such src properties in the CSS parser.

This makes the custom fonts used on http://apple.com/ actually load. :^)

Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp

@@ -4453,7 +4453,14 @@ Vector<FontFace::Source> Parser::parse_font_face_src(TokenStream<ComponentValue>
             continue;
         }
 
-        // FIXME: Implement `local()`.
+        if (first.is_function() && first.function().name().equals_ignoring_ascii_case("local"sv)) {
+            if (first.function().values().is_empty()) {
+                continue;
+            }
+            supported_sources.empend(first.function().values().first().to_string(), Optional<FlyString> {});
+            continue;
+        }
+
         dbgln_if(CSS_PARSER_DEBUG, "CSSParser: @font-face src invalid (failed to parse url from: {}); discarding.", first.to_debug_string());
         return {};
     }