Added multibranch support

[KDean-Dolphin]

Multibranch support now available in action.yml. Three parameters have been added:

• include-branches
  • If true, includes non-default branch publication to the "_branch/<branch_name>" path; ignored if include-pages is false.
• default-branch:
  • Default branch for include-branches to filter; ignored if include-branches is false.
  • Default is "main".
• pages-archive
  • Pages archive name; ignored if include-branches is false.
  • Default is "_pages".
  • Temporary directory with this name will be created during build and ZIP file with this name will be published to the root.