feat: add PageContainer::getPage

This allows us to directly access a page from outside. This will be
useful for telling the ManagedPackPage who is the window it's on, so
that we can close it when updating :^)

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

launcher/ui/pages/BasePageContainer.h

@@ -1,10 +1,13 @@
 #pragma once
 
+class BasePage;
+
 class BasePageContainer
 {
 public:
     virtual ~BasePageContainer(){};
     virtual bool selectPage(QString pageId) = 0;
+    virtual BasePage* getPage(QString pageId) { return nullptr; };
     virtual void refreshContainer() = 0;
     virtual bool requestClose() = 0;
 };

launcher/ui/widgets/PageContainer.cpp

@@ -130,6 +130,11 @@ bool PageContainer::selectPage(QString pageId)
     return false;
 }
 
+BasePage* PageContainer::getPage(QString pageId)
+{
+    return m_model->findPageEntryById(pageId);
+}
+
 void PageContainer::refreshContainer()
 {
     m_proxyModel->invalidate();

launcher/ui/widgets/PageContainer.h

@@ -79,6 +79,7 @@ public:
     }
 
     virtual bool selectPage(QString pageId) override;
+    BasePage* getPage(QString pageId) override;
 
     void refreshContainer() override;
     virtual void setParentContainer(BasePageContainer * container)