feat(readme.md): add a way to change settings without restarting the script
feat(readme.md): add a more detailed tutorial on how to use the script & readme
feat(readme.md): add a generator for more beautiful thumbnails
feat(readme.md): add a way to change the background music / add a way to add more background music / add a way to have channel specific background music
feat(readme.md): make the script prompts optionally channel specific for marp heading and oîdeas prompts
refactor(montage.py): use os.path.join instead of string concatenation
refactor(thumbnail.py): use os.path.join instead of string concatenation
refactor(uploader.py): use os.path.join instead of string concatenation
refactor(uploader.py): add support for client_secret.json file with different names in credentials folder
docs(readme.md): update instructions for openai and unsplash keys
docs(readme.md): update instructions for google oauth client id json files
docs(readme.md): add information about channel.yaml file in each channel's folder
