Add release notes section in github template
Add release notes section in github template

Hopefully, this will make it easier for Kirsten to fill in the release
notes from all the pull requests included in a release.

Em-AK/openfoodnetwork,openfoodfoundation/openfoodnetwork,lin-d-hop/openfoodnetwork,Em-AK/openfoodnetwork,KateDavis/openfoodnetwork,KateDavis/openfoodnetwork,Matt-Yorkley/openfoodnetwork,openfoodfoundation/openfoodnetwork,Matt-Yorkley/openfoodnetwork,lin-d-hop/openfoodnetwork,oeoeaio/openfoodnetwork,Matt-Yorkley/openfoodnetwork,oeoeaio/openfoodnetwork,mkllnk/openfoodnetwork,oeoeaio/openfoodnetwork,mkllnk/openfoodnetwork,openfoodfoundation/openfoodnetwork,oeoeaio/openfoodnetwork,KateDavis/openfoodnetwork,mkllnk/openfoodnetwork,KateDavis/openfoodnetwork,lin-d-hop/openfoodnetwork,Em-AK/openfoodnetwork,Matt-Yorkley/openfoodnetwork,Em-AK/openfoodnetwork,openfoodfoundation/openfoodnetwork,lin-d-hop/openfoodnetwork,mkllnk/openfoodnetwork