Document Go template's multiline support

Closes #764

content/en/templates/introduction.md

@@ -68,6 +68,22 @@ Accessing the Page Parameter `bar` defined in a piece of content's [front matter
 {{ if or (isset .Params "alt") (isset .Params "caption") }} Caption {{ end }}
 ```
 
+#### A Single Statement Can be Split over Multiple Lines
+
+```go-html-template
+{{ if or 
+  (isset .Params "alt") 
+  (isset .Params "caption")
+}}
+```
+
+#### Raw String Literals Can Include Newlines
+
+```go-html-template
+{{ $msg := `Line one.
+Line two.` }}
+```
+
 ## Variables {#variables}
 
 Each Go Template gets a data object. In Hugo, each template is passed