UX: Links to help during installation should open in new window to not break the flow

Problem/Motivation

In response to:
http://www.youtube.com/watch?v=7uSsnls16q0

Added target="_blank" to all links in install.php.

Steps to reproduce

Proposed resolution

Update links as needed according to the Accessibility core gate → . In particular, the use of WCAG 2.1, Opening new windows and tabs from a link only when necessary

Remaining tasks

Review the links
If any need to be changed, then create an MR.
review

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet