Extensions should find pmc links

[brandonStell]

Here is an example of a page with a link that is not found by the extension:
https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=TGF-Beta+suppresses+VEGFA-mediated+angiogenesis+in+colon+cancer+metastasis&btnG=

• I beleive that we already have the PMCIDs in the identifiers table of the db (to be confirmed with @XavRsl )
• They could be used to create urls in the publication_urls table
  https://www.ncbi.nlm.nih.gov/pmc/articles/ + PMCID + /

[jrobindev]

I see, will make the seeder class to fill the PMCID publication URLs.

[oganm]

I believe the browser extension still does not support links that lead to pubmed. This would be fairly useful for our purposes where we want pubpeer addon to work for our website but our data structure only contains the pmid urls and PMID ids. PMID ids work when they are present on their own but due to the exclusion here they cease to work if the same page also has valid DOIs.

It would be helpful if this exclusion of PMIDs when DOIs are present did not exist unless it's somehow necessary for something else, failing that it would be helpful for links to pubmed be recognized