added basic version fetching

src/singletons/updatemanager.hpp

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <QString>;
+#include <pajlada/signals/signal.hpp>
+
+namespace chatterino {
+namespace singletons {
+
+class UpdateManager
+{
+    UpdateManager();
+
+public:
+    static UpdateManager &getInstance();
+
+    void checkForUpdates();
+    const QString &getCurrentVersion() const;
+    const QString &getOnlineVersion() const;
+
+    pajlada::Signals::Signal onlineVersionUpdated;
+
+private:
+    QString currentVersion;
+    QString onlineVersion;
+};
+
+}  // namespace singletons
+}  // namespace chatterino