feat: add (semi) instant searching in mod downloader

It has a delay of 350ms from the last typed character to search, in
order to cache small changes while typing.

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/ui/pages/modplatform/ModPage.h

@@ -81,4 +81,7 @@ class ModPage : public QWidget, public BasePage {
     std::unique_ptr<ModAPI> api;
 
     int selectedVersion = -1;
+
+    // Used to do instant searching with a delay to cache quick changes
+    QTimer m_search_timer;
 };