Added loading spinners and preprocessed main dataframe

dash_plot_generation/data_store.py

dash_plot_generation/pages/dash_plot_generator.py

dash_plot_generation/precalculated_data/developer_list

...lot_generation/precalculated_data/game_popularity_filters

dash_plot_generation/precalculated_data/genre_list

dash_plot_generation/precalculated_data/main_dataframe

dash_plot_generation/precalculated_data/publisher_list

dash_plot_generation/semantic_layer.py

dash_plot_generation/styles_and_handles.py

dash_plot_generation/utils.py