Document examples of directives with only named args (#5755) [ci skip]

Signed-off-by: Ben Sherman <[email protected]>

docs/process.md

@@ -1128,12 +1128,12 @@ The `emit` option can be used on a process output to define a name for the corre
 process FOO {
     output:
     path 'hello.txt', emit: hello
-    path 'bye.txt', emit: bye
+    stdout emit: bye
 
     script:
     """
     echo "hello" > hello.txt
-    echo "bye" > bye.txt
+    echo "bye"
     """
 }
 

docs/reference/syntax.md

@@ -795,6 +795,9 @@ printf 'Hello %s!\n', 'World'
 
 // positional and named args
 file 'hello.txt', checkIfExists: true
+
+// named args
+resourceLabels group: 'my-group', user: 'me'
 ```
 
 If the last argument is a closure, it can be specified outside of the parentheses: