feat(docs): update docs (#563)

feat(docs): update docs

Updates the Wing docs. See details in [workflow run].

[Workflow Run]: https://github.com/winglang/docsite/actions/runs/5813749072

------

*Automatically created via the "update-docs" workflow*

versioned_docs/version-latest/03-language-reference.md

@@ -2,6 +2,7 @@
 title: Wing Programming Language Reference
 id: language-reference
 description: The Wing Language Reference
+sidebar_label: Language Reference
 keywords: [Wing reference, Wing language, language, Wing language spec, Wing programming language]
 ---
 
@@ -1543,11 +1544,18 @@ f(1, 2, field1: 3, field2: 4);
 // f(1, 2, field1: 3); // can't do this, partial expansion is not allowed
 ```
 
-#### 3.6.3 Roadmap
-
-The following features are not yet implemented, but we are planning to add them in the future:
-
-* Variadic arguments (`...args`) - see https://github.com/winglang/wing/issues/125 to track.
+#### 3.6.3 Variadic Arguments
+When a function signature's final parameter is denoted by `...` and annotated as an `Array` type,
+then the function accepts typed variadic arguments. 
+Inside the function, these arguments can be accessed using the designated variable name, 
+just as you would with a regular array instance.
+```TS
+let f = (x: num, ...args: Array<num>) => {
+  log("${x + args.length}");
+};
+// last arguments are expanded into their array
+f(4, 8, 15, 16, 23, 42); // logs 9
+```
 
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