I read that GitHub has some support for Jekyll plugins. With some difficulty I added the sitemap plugin that is supported.

First, I added - jekyll-sitemap under gems: in _config.yml and ran:

gem jekyll-sitemap

but this generated a number of error messages and no sitemap.

Next, I added gem "jekyll-sitemap", "~> 1.1.1" under group :jekyll_plugins do and after gem "jekyll-feed", "~> 0.6" and ran

gem install jekyll-sitemap

which didn’t work right. Then ran:

bundle install

After running:

bundle exec jekyll serve

I had a robots.txt file on my localhost _site that refered to sitemap.xml which contained references to localhost URLs. After deploying to GitHub the robots.txt links to sitemap.xml which use cygnyx.com in the URLs.

For SEO, I followed the instructions on jekyll-seo-tag. I added gem "jekyll-seo-tag", "~> 2.2.3" to Gemfile, - jekyll-seo-tag to _config.yml, and seo processing command in _includes/head.html before </head>. There are many parameters that control the META data in index.html, currently title and description are used.

I added a 16x16 shortcut icon by including this in the header:

  <link rel="shortcut icon" type="image/png" href="https://avatars2.githubusercontent.com/u/6766826?v=3&s=16">