Add ToggleEvent source (#3605)

Co-authored-by: Daniel D. Beck <[email protected]>

Author: tunetheweb

features/toggleevent-source.yml

@@ -0,0 +1,6 @@
+name: ToggleEvent source
+description: The `source` property of a `ToggleEvent` object is the element which triggered the `toggle` event to fire for a popover, `<dialog>`, or `<details>` element, if applicable.
+spec: https://html.spec.whatwg.org/multipage/interaction.html#dom-toggleevent-source
+group: html
+compat_features:
+  - api.ToggleEvent.source

features/toggleevent-source.yml.dist

@@ -0,0 +1,13 @@
+# Generated from: toggleevent-source.yml
+# Do not edit this file by hand. Edit the source file instead!
+
+status:
+  baseline: false
+  support:
+    chrome: "140"
+    chrome_android: "140"
+    edge: "140"
+    firefox: "145"
+    firefox_android: "145"
+compat_features:
+  - api.ToggleEvent.source