Update publications.html

[klein21]

Beginning work to update PCMDI publications page

[klein21]

@mauzey1
@durack1

Here's a start. I have about half of the 2021 publications in java for publications.html. If this works ok, then you can convert to Markdown and I will add the rest. If there are too many mistakes in what I did, feel free to abandon it, and convert the original publications.html to markdown without my changes.