some pages still don't work with CORS updates

[rgetz]

the html page in:
https://github.com/analogdevicesinc/buildroot/blob/rgetz-index.html-tweet/board/pluto/msd/index.html

when encoded with htmlpreview:
https://htmlpreview.github.io/?https://github.com/analogdevicesinc/buildroot/blob/rgetz-index.html-tweet/board/pluto/msd/index.html
shows a non-css version for a short time, and then blanks to a screen of all white (Chrome Version 73.0.3679.0 (Official Build) dev (64-bit)) Same happens in Firefox

[rgetz]

Same things are still happening in Chrome with:

http://htmlpreview.github.io/?https://github.com/analogdevicesinc/buildroot/blob/pluto/board/pluto/msd/index.html

• shows a non-css version for a second,
• shows a rendered version for a second
• throws a js error:

Uncaught (in promise) TypeError: Cannot read property 'appendChild' of null
    at loadJS (htmlpreview.js:85)
    at htmlpreview.js:56

• and then blank screen

On Edge - it displays a non-css version.

[MrCreosote]

I'm seeing slightly different behavior in FF66.0.5:
http://htmlpreview.github.io/?https://github.com/kbaseapps/DataFileUtil/blob/master/DataFileUtil.html
just shows up without CSS, but doesn't blank out to white.