build(vendor): migrate JUCE webkit2gtk from 4.0 to 4.1

Update all vendored JUCE 7.0.12 references from webkit2gtk-4.0 to
webkit2gtk-4.1: pkg-config targets, dynamic library names, docs, and
Projucer project exporter. The 4.0 API is removed in current Linux
distributions.

third_party/JUCE/modules/juce_gui_extra/native/juce_WebBrowserComponent_linux.cpp

@@ -206,7 +206,7 @@ private:
     }
 
     //==============================================================================
-    DynamicLibrary gtkLib { "libgtk-3.so" }, webkitLib { "libwebkit2gtk-4.0.so" };
+    DynamicLibrary gtkLib { "libgtk-3.so" }, webkitLib { "libwebkit2gtk-4.1.so" };
     const bool webKitIsAvailable = loadWebkitSymbols() && loadGtkSymbols();
 
     JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (WebKitSymbols)