Update to the latest release of GCWeb theme for Jekyll

[anthonyfok]

OpenDRR/data has mixed in multiple versions of GCWeb Jekyll, and thus the theme appears inconsistent, e.g. different colours...
It would be nice to upgrade to the latest GCWeb theme for Jekyll.

Looks like Joost is already working on it, e.g. the recently PR #41 GCWeb jekyll migration (due to the boilerplate being archived)...

Upstream GCWeb Jekyll related repos:

• https://github.com/wet-boew/gcweb-jekyll
• https://github.com/canada-ca/canada-ca-jekyll-boilerplate
  • Last changed in November 2020. Archived recently? (Between February and May 2021)

Some related upstream issues:

• boilerplate broken by latest wet-boew/gcweb-jekyll updates: Layout 'page' does not exist. canada-ca/canada-ca-jekyll-boilerplate#11
• Can't navigate from splash page on the demo site wet-boew/gcweb-jekyll#11
• Latest renaming/removal of layouts introduce breaking changes that should be documented wet-boew/gcweb-jekyll#21
• Use of assets: "https://wet-boew.github.io/themes-dist" led to 404 breakage wet-boew/gcweb-jekyll#23
• Missing assets wet-boew/gcweb-jekyll#24
• https://github.com/wet-boew/gcweb-jekyll/pulls/25

[jvanulde]

Closing. Migration completed in #41