Update pull request template (#4087)
Update pull request template (#4087)

* Wrap general directions into an HTML comment so they are
  not visible in the PR if the user doesn't delete them
* Add template for information a user is supposed to provide
  in order to avoid getting empty descriptions
* Add note on CircleCI
helm/charts,rimusz/helm-charts,sd2k/charts,grugnog/charts,rimusz/helm-charts,lachie83/charts,caiwenhao/charts,rimusz/helm-charts,sd2k/charts,lachie83/charts,sd2k/charts,GaneshSPatil/charts,smelchior/charts,grugnog/charts,rimusz/helm-charts,GaneshSPatil/charts,helm/charts,helm/charts,helm/charts,smelchior/charts,viglesiasce/charts,jainishshah17/charts,GaneshSPatil/charts,jainishshah17/charts,jainishshah17/charts,smelchior/charts,lachie83/charts,sd2k/charts,viglesiasce/charts,grugnog/charts,caiwenhao/charts,lachie83/charts,GaneshSPatil/charts,caiwenhao/charts,viglesiasce/charts