Download and convert MeSH *.nt files to SQLite databases.

Refer to the following link for more information on MeSH data:

https://id.nlm.nih.gov/mesh/

MeSH *nt files can be downloaded from relevant sub-folders found in this link:

https://nlmpubs.nlm.nih.gov/projects/mesh/rdf/

For instance, MeSH data for 2022 can be found here:

https://nlmpubs.nlm.nih.gov/projects/mesh/rdf/2022/