remove/polyfil prompt() from meta_keyframes and timeline.js

[steam0r]

electron does not have it: https://cables.gl/errorReport/672b50eec7e33d547aae4616 https://github.com/electron/electron/issues/472

[pandrr]

can be replaced like this:

        new ModalDialog({
            "prompt": true,
            "title": "Animation Length",
            "text": "Project length in frames:",
            "promptValue": 123,
            "promptOk": function (inputStr)
            {
            } });

[pandrr]

removed the prompts