feat: implement creating a new file

Merge branch 'feat/new-file' from
https://gitea.treehouse.systems/fortressia/echidna.git

See #20

src/components/window/file.rs

@@ -14,6 +14,7 @@ pub trait FileImplementedEditor {
     fn action_open_file(&self);
     fn open_file(notebook: &gtk::Notebook, file: gio::File);
     fn action_save_file_as(&self);
+    fn action_new_file(&self);
     fn action_save_file(&self);
 }
 
@@ -102,6 +103,14 @@ impl FileImplementedEditor for super::EchidnaWindow {
             }));
     }
 
+    fn action_new_file(&self) {
+        let editor_page = EchidnaCoreEditor::new(None);
+
+        self.to_imp()
+            .notebook
+            .prepend_closable_page(&editor_page, Some(&gtk::Label::new(Some(&"Untitled"))));
+    }
+
     fn action_save_file(&self) {
         let page: EchidnaCoreEditor = self
             .get_current_tab()

src/components/window/menubar.rs

@@ -122,6 +122,16 @@ impl MenubarImplementedEditor for EchidnaWindow {
                     window.action_save_file_as();
             }));
         }
+        {
+            let action_new_file = SimpleAction::new("new-file", None);
+
+            self.add_action(&action_new_file);
+
+            action_new_file.connect_activate(clone!(@weak self as window =>
+                move |_action, _variant| {
+                    window.action_new_file();
+            }));
+        }
         {
             let action_save = SimpleAction::new("save", None);