Update to work with latest DecapCMS and minor feature tweaks

[anjackson]

I wanted to use this module with the latest version of DecapCMS, which depends on React 19. I could not get the build to work, and would get strange React errors when deploying the module, so I followed the example of https://github.com/iamspark1e/decap-cms-widget-starter and switched to Vite. I also added a configuration option to make the ability to regenerate the ID an optional thing rather than always being available.

If you'd rather not switch to Vite I can try to get Webpack working, but I may need some assistance in that case. Sorry about that!

[anjackson]

I went back and checked what my original problem was, and if I build this module using the babel command provided, I get errors like Uncaught SyntaxError: The requested module './index.js' does not provide an export named 'Widget' when I try to use it as a module, and errors that complain about using require otherwise.