add missing head_extras block

[snokamedia]

added missing head_extras block used in default templates ckan/templates/package/read_base.html and ckan/templates/package/resource_read.html

Features:

• [ ] includes tests covering changes
• [ ] includes updated documentation
• [ ] includes user-visible changes
• [ ] includes API changes
• [ ] includes bugfix for possible backport

[amercader]

Thanks @snokamedia this makes sense. Can you restore the body_extras block as well? It is still used in at least one extension out there. It should go here.

These blocks were removed in #7672 . The removal of the config options made sense but the blocks should have been left there as they were used by other templates.

[ckanbot]

Successfully created backport PR for dev-v2.11:

• #8403