Fixes for inconsistent state loading

[EdwardMoyse]

Now, let me clearly state that I do not precisely know what is going on here!

However, as discussed in various tickets (specifically #582, but possibly also others), loading files has been very unreliable. In #603 I tried to add a wait, which seemed to help, but which recently (new Safari version?) became less effective.

After a lot of googling, it seems like this is a known issue in Safari - the onchange event never gets called/sent, with the consequence that the file is never loaded.

The changes to inputFile.onclick and invalid are supposed to be failsafes. I think they probably aren't actually needed, but I have left them in case.

What I think might have been happening is that inputfile was either being deleted before the callback could happen (which is why the wait added in #603 helped). And I also noticed that inputfile sometimes seemed to hang around.

So I thought adding it to the document might help with these kinds of issues - so I believe this is the real fix:

 const inputFile = document.createElement('input');
  document.body.appendChild(inputFile);

This PR also contains a fix for a deprecation in TextGeometry in recent threejs versions.