Adds builds to CI for pushes to main

[DrPaulSharp]

Description

Modifies the CI to also create and test a build for pushes to main. We may want a more elegant approach to this, but this should fix our CI problems for now.

Fixes #3915

How Has This Been Tested?

Test requires a merge.

Review Checklist:

[if using the editor, use [x] in place of [ ] to check a box]

Documentation (check at least one)

• There is nothing that needs documenting
• Documentation changes are in this PR
• There is an issue open for the documentation (link?)

Installers

• There is a chance this will affect the installers, if so
  • Windows installer (GH artifact) has been tested (installed and worked)
  • MacOSX installer (GH artifact) has been tested (installed and worked)
  • Wheels installer (GH artifact) has been tested (installed and worked)

Licensing (untick if necessary)

• The introduced changes comply with SasView license (BSD 3-Clause)

[DrPaulSharp]

Closed in favour of #3916

[DrPaulSharp]

#3916 didn't work, so reopening here.

[krzywon]

This should fix the issue, but the check might be slightly more specific than we need.