Add the possibility to save and create a new page

[giuscris]

This pull request introduces a new "Save and create new" feature to the page editor, allowing users to quickly save their current page and immediately start creating a new one. It also includes UI and backend changes to support this workflow, along with minor improvements to the modal and translation files.

New "Save and create new" workflow:

• Added a "Save and create new" button to the page editor dropdown, enabling users to save the current page and open the new page modal in a single action. [1] [2]
• Updated backend logic in PagesController.php to handle the createNew query parameter, open the new page modal automatically when appropriate, and ensure redirects preserve the new workflow. [1] [2]

Frontend improvements:

• Enhanced the pages view script to clean up the createNew query parameter from the URL after opening the modal, preventing unwanted repeated modal openings on refresh.

Localization:

• Added a new translation string for the "Save and create new" action in the English language file.