Add search predicates for badges and sub tiers (#4013)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

src/messages/search/BadgePredicate.hpp

@@ -0,0 +1,38 @@
+#pragma once
+
+#include "messages/search/MessagePredicate.hpp"
+
+namespace chatterino {
+
+/**
+ * @brief MessagePredicate checking for the badges of a message.
+ *
+ * This predicate will only allow messages that are sent by a list of users,
+ * specified by their user names, who have a badge specified (i.e 'staff').
+ */
+class BadgePredicate : public MessagePredicate
+{
+public:
+    /**
+     * @brief Create an BadgePredicate with a list of badges to search for.
+     *
+     * @param badges a list of badges that a message should contain 
+     */
+    BadgePredicate(const QStringList &badges);
+
+    /**
+     * @brief Checks whether the message contains any of the badges passed
+     *        in the constructor.
+     *
+     * @param message the message to check
+     * @return true if the message contains a badge listed in the specified badges,
+     *         false otherwise
+     */
+    bool appliesTo(const Message &message) override;
+
+private:
+    /// Holds the badges that will be searched for
+    QStringList badges_;
+};
+
+}  // namespace chatterino