Extract TooltipWidget updating into a separate class

src/singletons/TooltipPreviewImage.hpp

@@ -0,0 +1,18 @@
+#pragma once
+
+#include "messages/Image.hpp"
+
+namespace chatterino {
+    class TooltipPreviewImage {
+    public:
+        static TooltipPreviewImage &getInstance();
+        void setImage(ImagePtr image);
+
+    private:
+        TooltipPreviewImage();
+
+    private:
+        ImagePtr image_ = nullptr;
+        std::vector<pajlada::Signals::ScopedConnection> connections_;
+    };
+}  // namespace chatterino