Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/21733
Add two newlines before the template if the existing description isn't
empty. This makes it easier to see where the template begins.
Don't append the template when "Reset template" is selected, of course.
Don't append template if it equals the existing description. This makes
it so that selecting a template twice doesn't duplicate it.
Trigger autosize update after template selection
## What does this MR do?
Triggers an autosize update after selecting an issue template.
The autosize plugin doesn't react to value changes and therefore doesn't automatically update when the user selects the template. This merge request adds it so that it detects if the editor the template selector is a jQuery object (not Ace editor) & then triggers the autosize event to allow the user to scroll the textarea.
## Screenshots (if relevant)
## What are the relevant issue numbers?
Closes#21982
See merge request !6282
