Improve sink and spreading docs

docs/reference/syntax.md

@@ -85,6 +85,7 @@ a table listing all syntax that is available in code mode:
 | Field access             | `{x.y}`                       | [Scripting]($scripting/#fields)    |
 | Method call              | `{x.flatten()}`               | [Scripting]($scripting/#methods)   |
 | Function call            | `{min(x, y)}`                 | [Function]($type/function)         |
+| Argument spreading       | `{min(..nums)}`               | [Arguments]($type/arguments)       |
 | Unnamed function         | `{(x, y) => x + y}`           | [Function]($type/function)         |
 | Let binding              | `{let x = 1}`                 | [Scripting]($scripting/#bindings)  |
 | Named function           | `{let f(x) = 2 * x}`          | [Function]($type/function)         |

docs/reference/types.md

@@ -1066,26 +1066,36 @@ whose fields have the values of the given arguments.
 # Arguments
 Captured arguments to a function.
 
+## Argument Sinks
 Like built-in functions, custom functions can also take a variable number of
 arguments. You can specify an _argument sink_ which collects all excess
 arguments as `..sink`. The resulting `sink` value is of the `arguments` type. It
-exposes methods to access the positional and named arguments and is iterable
-with a [for loop]($scripting/#loops). Inversely, you can spread
-arguments, arrays and dictionaries into a function call with the spread operator:
-`{func(..args)}`.
+exposes methods to access the positional and named arguments.
 
-## Example
 ```example
-#let format(title, ..authors) = [
-  *#title* \
-  _Written by #(authors
+#let format(title, ..authors) = {
+  let by = authors
     .pos()
-    .join(", ", last: " and "));._
-]
+    .join(", ", last: " and ")
+
+  [*#title* \ _Written by #by;_]
+}
 
 #format("ArtosFlow", "Jane", "Joe")
 ```
 
+## Spreading
+Inversely to an argument sink, you can _spread_ arguments, arrays and
+dictionaries into a function call with the `..spread` operator:
+
+```example
+#let array = (2, 3, 5)
+#calc.min(..array)
+
+#let dict = (fill: blue)
+#text(..dict)[Hello]
+```
+
 ## Methods
 ### pos()
 Returns the captured positional arguments as an array.