Release 0.3.0

[larnsce]

Summary

• Releases washopenresearch 0.3.0: bumps the version, sets the release date, and rolls the development NEWS section into the 0.3.0 heading.
• Updates DESCRIPTION and regenerates CITATION.cff with cffr so both list all four datasets (washdev, uncnewsletter, ploswater, datapapers); the Zenodo DOI and keywords are preserved and a preferred-citation block is added.

Test plan

• NEWS.md top heading reads "washopenresearch 0.3.0" and matches the DESCRIPTION version
• CITATION.cff validates (cffr::cff_validate())
• Rscript -e 'devtools::load_all()' succeeds