Improves keywords retrieve

Improves keywords retrieve

Show primary locale keywords when current locale keywords are empty

Show primary locale keywords when current locale keywords are empty

Normalize keywords to lowercase and removes duplicates (OJS/OMP 3.4)

Normalize keywords to lowercase and removes duplicates

Adapts plugin to OJS 3.4.0

Fixes method to retrive context.

Update block title to `h2`

Fix cache dismiss error