templates: Document `httpError` function (#4972)
templates: Document `httpError` function (#4972)

* added the httpError function into the document

* Update templates.go

* Update templates.go

* Fix gofmt

Co-authored-by: Matt Holt <6e15340bc34d98c823445cca0475cc9127379d4b@users.noreply.github.com>
l3dlp/caddy,l3dlp/caddy,l3dlp/caddy