Add a changeset for event-target

Author: matthewp

.changeset/stupid-beds-draw.md

@@ -0,0 +1,51 @@
+---
+"corset": minor
+---
+
+Allow specifying an alternative event target with event-target
+
+This now allows specifying an alternative event target via the new `event-target` property. You can use it like this:
+
+```js
+import sheet, { mount } from 'https://cdn.corset.dev/v2';
+
+mount(document, class {
+  onpopstate(ev) {
+    console.log(`location: ${document.location}, state: ${JSON.stringify(event.state)}`);
+  }
+  bind() {
+    return sheet`
+      #app {
+        event: popstate ${this.onpopstate};
+        event-target: popstate ${window};
+      }
+    `;
+  }
+});
+```
+
+In the above we are able to use a selector to listen to the [popstate](https://developer.mozilla.org/en-US/docs/Web/API/Window/popstate_event) event that is on the window object.
+
+This can also be used with any object that follows the [EventTarget](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget) interface:
+
+```js
+import sheet, { mount } from 'https://cdn.corset.dev/v2';
+
+let target = new EventTarget();
+// Now this can be shared around
+
+mount(document, class {
+  bind() {
+    return sheet`
+      #app {
+        event: foo ${() => console.log('foo event occurred!')};
+        event-target: foo ${target};
+      }
+
+      some-custom-element {
+        prop: events ${target};
+      }
+    `;
+  }
+});
+```