Add URL checks to Doctor (#5760)
Add URL checks to Doctor (#5760)

Merge pull request 5760
jekyll/jekyll,jaybe-jekyll/jekyll,x-way/jekyll,tillgrallert/jekyll,getandpost/jekyll.github.io,alex-kovac/jekyll,chrisfinazzo/jekyll,fulldecent/jekyll,x-way/jekyll,getandpost/jekyll.github.io,gencer/jekyll,jekyll/jekyll,tillgrallert/jekyll,ryanshaw/jekyll,jaybe-jekyll/jekyll,fulldecent/jekyll,gencer/jekyll,chrisfinazzo/jekyll,jekyll/jekyll,yhironaka/yhironaka.github.io,Strangehill/jekyll,ryanshaw/jekyll,Strangehill/jekyll,tillgrallert/jekyll,alex-kovac/jekyll,jekyll/jekyll,tillgrallert/jekyll,jaybe-jekyll/jekyll,Strangehill/jekyll,fulldecent/jekyll,x-way/jekyll,Strangehill/jekyll,fulldecent/jekyll,gencer/jekyll,gencer/jekyll,getandpost/jekyll.github.io,alex-kovac/jekyll,gencer/jekyll,x-way/jekyll,jaybe-jekyll/jekyll,chrisfinazzo/jekyll,Strangehill/jekyll,alex-kovac/jekyll,chrisfinazzo/jekyll,alex-kovac/jekyll,tillgrallert/jekyll,ryanshaw/jekyll,ryanshaw/jekyll