You will note the `Cite this repository` link is not working.
This commit fixes the underlying file...
* `authors` was not indented
* `authors` required by `preferred-citation`
* `authors` list required at top level (I simply duplicated)
* `"USA"` not correct country code
* `month` requires an integer month number
* Added URL to the actual pdf of the cited paper
* Used `identifiers` for doi and LLNL doc number
* added `abstract` copied from paper
Various fixes were confirmed by `cffconvert` using `docker run -v `pwd`:/app citationcff/cffconvert --validate`
