[Custom Components] Option for build target

[radames]

Sorry if there is already an open issue for this, but here's a reminder to add the target: 'esnext' option when building custom components.

cc @pngwn

The currently workaround is do edit node_modules

go into your node modules/gradio/preview/dist/index.js
go into line ~278
add this in the build object: target: 'esnext',
then `gradio cc build ` again

[pngwn]

Thanks for this @radames, it did indeed slip my mind.

[freddyaboulton]

+1 just ran into this myself for the pdf component when trying to upgrade pdf.js