v3.5.0-alpha.1

Changes include:

• Allow opening URL with different origin in app.open_new_page().
• Add checkout using stripe and paypal
• Access firestore database using app.firestore attribute
• Add page-specific variables app.page_vars which stores data that is reset after the user leaves the page.
• Add app.get_current_url() which returns the current full URL.
• Add app.get_query_params which returns a dictionary of the current URL query parameters (or a different URL).
• Add more parameters in `app.redirect_response()
• Add app.get_users_ids_from_data.
• Add Element.get_class_list.
• Add Element.add_to_class_list
• Add Element.remove_from_class_list.
• Add example about creating "widgets"
• Some fixes related to signing up and signing in
• Fix Element.from_str
• Fix Element.set_content and Element.add_content

Full Changelog: v3.4.0...v3.5.0-alpha.1