Docs: fix code syntax highlighting in Core docs
Merge pull request #4354 from patheard/docs-core

Docs: fix code syntax highlighting in Core docs
Documentation: Moved promotional material to HTML pages and fixed up metadata
Merge pull request #4356 from pjackson28/movecommunicationsmaterials

Documentation: Moved promotional material to HTML pages and fixed up metadata
Docs: add GCWU theme documentation
Docs: corrected plugin and polyfill  metadata
Merge pull request #4355 from patheard/docs-gcwu

Docs: add GCWU theme documentation
Merge pull request #4359 from patheard/docs-metadata

Docs: corrected plugin and polyfill  metadata
Docs: add GC Web Usability Intranet Theme documentation
Documentation: Fixed various broken ZIP links in downloads pages.
Merge pull request #4360 from patheard/docs-gcwu-intranet

Docs: add GC Web Usability Intranet Theme documentation
Merge pull request #4362 from EricDunsworth/v3.0-broken-link-fixes

Documentation: Fixed various broken ZIP links in downloads pages.
Corrected the metadata on the documentation and working examples pages
Merge pull request #4363 from pjackson28/moremetadatafixes

Corrected the metadata on the documentation and working examples pages
Enabled site search in v3.0
Merge pull request #4364 from pjackson28/enablesearch

Enabled site search in v3.0
Resolved merge conflicts