feat(html): add autofocus helper

Co-Authored-By: Virgil <virgil@lethean.io>

docs/architecture.md

@@ -39,6 +39,7 @@ Accessibility-oriented helpers are also provided for common attribute patterns:
 - `Alt(node, text)`
 - `AriaHidden(node, hidden)`
 - `TabIndex(node, index)`
+- `AutoFocus(node)`
 
 ### Safety Guarantees
 

node.go

@@ -192,6 +192,11 @@ func TabIndex(n Node, index int) Node {
 	return Attr(n, "tabindex", strconv.Itoa(index))
 }
 
+// AutoFocus sets the autofocus attribute on an element node.
+func AutoFocus(n Node) Node {
+	return Attr(n, "autofocus", "autofocus")
+}
+
 func (n *elNode) Render(ctx *Context) string {
 	if n == nil {
 		return ""

node_test.go

@@ -286,6 +286,15 @@ func TestTabIndexHelper(t *testing.T) {
 	}
 }
 
+func TestAutoFocusHelper(t *testing.T) {
+	ctx := NewContext()
+	node := AutoFocus(El("input"))
+	got := node.Render(ctx)
+	if !strings.Contains(got, `autofocus="autofocus"`) {
+		t.Errorf("AutoFocus() = %q, want autofocus=\"autofocus\"", got)
+	}
+}
+
 func TestElNode_MultipleAttrs(t *testing.T) {
 	ctx := NewContext()
 	node := Attr(Attr(El("a", Raw("link")), "href", "/home"), "class", "nav")