Add a new completion API for experimental plugins feature. (#5000)

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

src/controllers/plugins/PluginController.hpp

@@ -36,6 +36,7 @@ public:
     // This is required to be public because of c functions
     Plugin *getPluginByStatePtr(lua_State *L);
 
+    // TODO: make a function that iterates plugins that aren't errored/enabled
     const std::map<QString, std::unique_ptr<Plugin>> &plugins() const;
 
     /**
@@ -52,6 +53,10 @@ public:
      */
     static bool isPluginEnabled(const QString &id);
 
+    std::pair<bool, QStringList> updateCustomCompletions(
+        const QString &query, const QString &fullTextContent,
+        int cursorPosition, bool isFirstWord) const;
+
 private:
     void loadPlugins();
     void load(const QFileInfo &index, const QDir &pluginDir,
@@ -64,5 +69,5 @@ private:
     std::map<QString, std::unique_ptr<Plugin>> plugins_;
 };
 
-};  // namespace chatterino
+}  // namespace chatterino
 #endif