fix(lua): small lua / lau doc fixes (#2415)

* fix(lua): small lua / lau doc fixes: expose stats.get_character_index like intended. also add a bit of doc to button and sameline pages so that the user is correctly refered to the tab class doc

src/lua/bindings/gui/button.hpp

@@ -8,6 +8,7 @@ namespace lua::gui
 	// Name: button
 	// Inherit: base_text_element
 	// Class representing a gui button.
+	// Refer to the tab class documentation for more info (tab:add_button(name, callback))
 	class button : public base_text_element
 	{
 		sol::protected_function m_callback;

src/lua/bindings/gui/sameline.hpp

@@ -6,6 +6,7 @@ namespace lua::gui
 	// Lua API: Class
 	// Name: sameline
 	// Class for ImGui::SameLine() - Puts a sameline between widgets or groups to layout them horizontally.
+	// Refer to the tab class documentation for more info (tab:add_sameline())
 	class sameline : public gui_element
 	{
 	public: