Add custom image functionality for inline mod buttons. (#5369)

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/util/LoadPixmap.hpp

@@ -0,0 +1,15 @@
+#pragma once
+#include "common/Aliases.hpp"
+
+#include <QPixmap>
+
+namespace chatterino {
+
+/**
+ * Loads an image from url into a QPixmap. Allows for file:// protocol links. Uses cacheing.
+ *
+ * @param callback The callback you will get the pixmap by. It will be invoked concurrently with no guarantees on which thread.
+ */
+void loadPixmapFromUrl(const Url &url, std::function<void(QPixmap)> &&callback);
+
+}  // namespace chatterino