LearnDash LMS 4.15.0

* Feature - Customizer settings for the LearnDash 3.0 template.
* Fix - Fixed issue where adding directory index file causes PHP notices when the directory is not writable.
* Fix - Resolved issue where admins cannot disable all toggles in certain metaboxes.
* Fix - Resolved issue where Additional Question Options won't stay toggled on when only "Randomize Answers" is enabled.
* Fix - Resolved issue where Windows-based servers were unable to use the Import tool.
* Fix - Resolved issue where adding a percentage symbol in password in login form would change the password.
* Fix - Resolved issue where TrustedLogin access link doesn't auto log in the user.
* Tweak - Updated functions: `learndash_put_directory_index_file`.
* Tweak - Added filters: `learndash_customizer_config`, `learndash_customizer_control`, `learndash_customizer_css_priority`, `learndash_customizer_themes`.
* Tweak - Added actions: `learndash_customizer_control_add_after`, `learndash_customizer_control_add_before`, `learndash_customizer_panel_add_after`, `learndash_customizer_panel_add_before`, `learndash_customizer_section_add_after`, `learndash_customizer_section_add_before`, `learndash_customizer_setting_add_after`, `learndash_customizer_setting_add_before`, `learndash_customizer_themes_init_after`, `learndash_customizer_themes_init_before`, `learndash_customizer_theme_init_after`, `learndash_customizer_theme_init_before`.

* Feature - Added decimal and negative number support to quiz points.
* Feature - Added "Different points for each answer" option support to the quiz builder.
* Fix - Resolved issue where NaN points label could appear if points were deleted in the quiz builder.
* Fix - Fixed quiz statistics loading for quizzes where all questions are set to 0 points.
* Fix - Improved question and answer points synchronization in the quiz builder.
* Fix - Resolved issue where the question settings were ignored in the quiz builder when the existing question was added.
* Fix - Resolved issue where the question was being duplicated on deletion in the quiz builder sidebar in some cases.
* Fix - Resolved issue where the free choice question points are calculated incorrectly when the different points mode is enabled.
* Tweak - Added points calculation within the POST route in the `ldlms/v1/sfwd-questions/<id>` REST API endpoint.
* Tweak - Updated constants: WPPROQUIZ_VERSION.
* Tweak - Updated functions: `learndash_format_course_points`, `learndash_get_essay_details`, `learndash_proquiz_sync_question_fields`, `learndash_question_assessment_fetch_data`, `learndash_question_cloze_fetch_data`, `learndash_question_free_get_answer_data`, `learndash_update_quiz_statistics`.
* Tweak - Updated filters: `learndash_course_points_format_round`, `learndash_fetch_quiz_questions`, `learndash_ques_free_answer_pts`, `learndash_ques_multiple_answer_pts_each`, `learndash_ques_multiple_answer_pts_whole`, `learndash_ques_single_answer_pts`, `learndash_quiz_question_answer_preprocess`.
* Tweak - Updated templates: `legacy/templates/quiz/partials/show_quiz_questions_box.php`.

* Feature - LearnDash Experiments.
* Feature - Virtual Instructor [Experiment].
* Tweak - Added filters: `learndash_experiments`, `learndash_model_virtual_instructor_applied_to_all_courses`, `learndash_model_virtual_instructor_applied_to_all_groups`, `learndash_model_virtual_instructor_avatar_url`, `learndash_model_virtual_instructor_banned_words`, `learndash_model_virtual_instructor_course_ids`, `learndash_model_virtual_instructor_custom_instruction`, `learndash_model_virtual_instructor_error_message`, `learndash_model_virtual_instructor_group_ids`, `learndash_model_virtual_instructor_message_contains_banned_words`, `learndash_model_virtual_instructor_name`, `learndash_module_ai_chatgpt_summarizer_command_generate_summary`, `learndash_module_ai_chatgpt_summarizer_last_preserved_messages_count`, `learndash_module_ai_chatgpt_summarizer_max_context_characters`, `learndash_module_ai_chatgpt_summarizer_messages_summary_content`, `learndash_module_ai_virtual_instructor_chat_session_initial_message`, `learndash_module_ai_virtual_instructor_chat_session_max_message_length`, `learndash_module_ai_virtual_instructor_chat_session_message_is_valid`, `learndash_module_ai_virtual_instructor_chat_session_message`, `learndash_module_ai_virtual_instructor_chat_session_storage_period`, `learndash_service_chatgpt_model_max_context_window_tokens`, `learndash_template_template_paths`.
* Tweak - Added actions: `learndash_experiments_experiment_init_after`, `learndash_experiments_experiment_init_before`, `learndash_experiments_init_after`, `learndash_experiments_init_before`, `learndash_post_setting_updated`.