LibWeb+LibWebView+WebContent: Add an Inspector IPC to open context menus

The Inspector will have context menu support to manipulate the DOM, e.g.
adding or removing nodes/attributes. This context menu will require some
detailed knowledge about what element in the Inspector has been clicked.
To support this, we intercept the `contextmenu` event and collect the
required information to be sent to the Inspector client over IPC.

Userland/Libraries/LibWeb/Internals/Inspector.cpp

@@ -61,6 +61,11 @@ void Inspector::replace_dom_node_attribute(i32 node_id, String const& name, JS::
     global_object().browsing_context()->page().client().inspector_did_replace_dom_node_attribute(node_id, name, replacement_attributes);
 }
 
+void Inspector::request_dom_tree_context_menu(i32 node_id, i32 client_x, i32 client_y, String const& type, Optional<String> const& tag_or_attribute_name)
+{
+    global_object().browsing_context()->page().client().inspector_did_request_dom_tree_context_menu(node_id, { client_x, client_y }, type, tag_or_attribute_name);
+}
+
 void Inspector::execute_console_script(String const& script)
 {
     global_object().browsing_context()->page().client().inspector_did_execute_console_script(script);

Userland/Libraries/LibWeb/Internals/Inspector.h

@@ -25,6 +25,8 @@ public:
     void set_dom_node_tag(i32 node_id, String const& tag);
     void replace_dom_node_attribute(i32 node_id, String const& name, JS::NonnullGCPtr<DOM::NamedNodeMap> replacement_attributes);
 
+    void request_dom_tree_context_menu(i32 node_id, i32 client_x, i32 client_y, String const& type, Optional<String> const& tag_or_attribute_name);
+
     void execute_console_script(String const& script);
 
 private:

Userland/Libraries/LibWeb/Internals/Inspector.idl

@@ -9,6 +9,8 @@
     undefined setDOMNodeTag(long nodeID, DOMString tag);
     undefined replaceDOMNodeAttribute(long nodeID, DOMString name, NamedNodeMap replacementAttributes);
 
+    undefined requestDOMTreeContextMenu(long nodeID, long clientX, long clientY, DOMString type, DOMString? tagOrAttributeName);
+
     undefined executeConsoleScript(DOMString script);
 
 };