database: pagedao: Add findByTitle()

database/pagedao.h

@@ -13,6 +13,7 @@ class PageDao
 	virtual bool exists(std::string page) const = 0;
 	virtual bool exists(unsigned int id) const = 0;
 	virtual std::optional<Page> find(std::string name) = 0;
+	virtual std::optional<Page> findByTitle(std::string title) = 0;
 	virtual std::optional<Page> find(unsigned int id) = 0;
 	virtual std::vector<std::string> getPageList(QueryOption option) = 0;
 	virtual std::vector<std::string> fetchCategories(std::string pagename, QueryOption option) = 0;