* origin/master: (65 commits)
Update history to reflect merge of #4703 [ci skip]
Update history to reflect merge of #4712 [ci skip]
Highlight the test code
Update history to reflect merge of #4640 [ci skip]
readded "env=prod"-condition
Update history to reflect merge of #3849 [ci skip]
Update history to reflect merge of #4624 [ci skip]
Update history to reflect merge of #4704 [ci skip]
Update history to reflect merge of #4706 [ci skip]
Checks for link file extension in tests
Updating assets documentation
Fix test teardown for cleaner.
Update history to reflect merge of #4542 [ci skip]
Add explanation of site variables in the example _config.yml
Use double quotes in the gemfile
Add test for creation of Gemfile by 'jekyll new'
Add comment about github-pages
Update history to reflect merge of #4533 [ci skip]
Ensure Rouge closes its div/figure properly after highlighting ends.
Add Site#config= which can be used to set the config
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