[ticket/12301] Template Event overall_header_body_before

add template event overall_header_body_before

PHPBB3-12301
Merge remote-tracking branch 'prosk8er/ticket/12301' into develop-ascraeus

* prosk8er/ticket/12301:
  [ticket/12301] Template Event overall_header_body_before
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12301] Template Event overall_header_body_before