Add OAI-PMH

[rdmpage]

Suggestion from Lyubo to harvest Pensoft OAI-PMH https://arphahub.com/about/OAI-PMH

From taxacom https://taxacom.markmail.org/thread/5lx4qsnbspym27me

Regarding Pensoft and some points raised by others in this tread, I think
that you can use also OAI-PMH, besides RSS, to harvest all content from
one-stop web service end point (see ours at:
https://arphahub.com/about/OAI-PMH). Through OAI-PMH you can also select
Pensoft's ca. 20+ journals that publish taxonomic records (not just ZooKeys
or PhytoKes). The high-level taxa associated to each article can be taken
from the * *in each article XML. RSS are fine and great,
however they cover only the last 100 newly published items and not always
give straightforward access to the full-text article XML. In other words,
you have to rely mostly on metadata in this case.