Add feature to download PMIDs generated via PubMed search

[scarioscia]

Adds a flag --search that allows direct query of PubMed from the command line. The resulting PMIDs are then passed to existing code for download.

• --search flag optionally replaces --pmids and --pmidsfile
• Takes search terms as string
• Requires Entrez from the Bio library to access NCBI search

Example executable: python3 -m pubmed2pdf pdf --search "ovule count flower"

By using --search, users can directly download the PDFs corresponding to their inquiry rather than externally generating a list of PMIDs through a separate step.