Add Element.attachShadow() option slotAssignment (#29681)

Element.attachShadow() - option.slotAssignment

Author: hamishwillee

api/Element.json

@@ -2948,6 +2948,41 @@
               "deprecated": false
             }
           }
+        },
+        "options_slotAssignment_parameter": {
+          "__compat": {
+            "description": "`options.slotAssignment` parameter",
+            "spec_url": "https://dom.spec.whatwg.org/#dom-shadowrootinit-slotassignment",
+            "tags": [
+              "web-features:shadow-dom"
+            ],
+            "support": {
+              "chrome": {
+                "version_added": "86"
+              },
+              "chrome_android": "mirror",
+              "edge": "mirror",
+              "firefox": {
+                "version_added": "92"
+              },
+              "firefox_android": "mirror",
+              "oculus": "mirror",
+              "opera": "mirror",
+              "opera_android": "mirror",
+              "safari": {
+                "version_added": "16.4"
+              },
+              "safari_ios": "mirror",
+              "samsunginternet_android": "mirror",
+              "webview_android": "mirror",
+              "webview_ios": "mirror"
+            },
+            "status": {
+              "experimental": false,
+              "standard_track": true,
+              "deprecated": false
+            }
+          }
         }
       },
       "attributes": {