Add ability to customize cache folder

Add an advanced settings page, currently only housing the "Cache" category

Fix #541

src/widgets/settingspages/AdvancedPage.hpp

@@ -0,0 +1,13 @@
+#pragma once
+
+#include "widgets/settingspages/SettingsPage.hpp"
+
+namespace chatterino {
+
+class AdvancedPage : public SettingsPage
+{
+public:
+    AdvancedPage();
+};
+
+}  // namespace chatterino