Adds download button for Panopto videos
This adds a green download button when on a Panopto video page.
It uses the Panopto video page title to create a valid filename, and copies the filename to the clipboard.
When the user clicks on the button, a new tab will open with the Panopto video as a .MP4 file.
The user can press Ctrl+S to open the "Save As" prompt, and paste the valid filename from the clipboard.
