[PLAT-993] Add BMJ journals to COS site

[Johnetordoff]

Purpose

We keep adding journals to our list of cool journals, especially BMJ journals. That means we need import them via migration. This migration does that.

Change

• adds JSON file for all BMJ files to be imported
• adds migration for all those JSON entries

QA

Check that all those journals are in there.

Documentation

Self-evident changes

Side effects

None that I know of.