Enumerate draggable attribute (preactjs#288)

* Enumerate draggable attribute

* Restore cross-env changes

* Restore package.json

* Create .changeset/fifty-hounds-press.md

---------

Co-authored-by: Jovi De Croock <[email protected]>

Author: glenchao

.changeset/fifty-hounds-press.md

@@ -0,0 +1,5 @@
+---
+"preact-render-to-string": patch
+---
+
+Enumerate draggable attribute, so the output isn't `draggable` but `draggable="true"`

src/index.js

@@ -311,8 +311,13 @@ function _renderToString(vnode, context, isSvgMode, selectValue, parent) {
 					name = name.toLowerCase().replace(XLINK_REPLACE_REGEX, 'xlink:');
 				} else if (UNSAFE_NAME.test(name)) {
 					continue;
-				} else if (name[0] === 'a' && name[1] === 'r' && v != null) {
-					// serialize boolean aria-xyz attribute values as strings
+				} else if (
+					((name[0] === 'a' && name[1] === 'r') || name === 'draggable') &&
+					v != null
+				) {
+					// serialize boolean aria-xyz or draggable attribute values as strings
+					// `draggable` is an enumerated attribute and not Boolean. A value of `true` or `false` is mandatory
+					// https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/draggable
 					v += '';
 				}
 			}

test/render.test.js

@@ -135,6 +135,13 @@ describe('render', () => {
 			expect(rendered).to.equal(expected);
 		});
 
+		it('should include boolean draggable attribute', () => {
+			let rendered = render(<div draggable />),
+				expected = `<div draggable="true"></div>`;
+
+			expect(rendered).to.equal(expected);
+		});
+
 		describe('attribute name sanitization', () => {
 			it('should omit attributes with invalid names', () => {
 				let rendered = render(