docs: major changeset

Author: bennypowers

.changeset/clear-pugs-make.md

@@ -1,5 +1,31 @@
 ---
-"@patternfly/pfe-core": patch
+"@patternfly/pfe-core": major
 "@patternfly/elements": patch
 ---
-Enable context protocol in SSR scenarios.
+Enable `connectedCallback()` and context protocol in SSR scenarios.
+
+BREAKING CHANGE
+This change affects any element which is expected to execute in node JS when
+lit-ssr shims are present. By enabling the `connectedCallback()` to execute
+server side. Elements must ensure that their connectedCallbacks do not try to
+access the DOM.
+
+Before:
+
+```js
+connectedCallback() {
+  super.connectedCallback();
+  this.items = this.querySelectorAll('my-item');
+}
+```
+
+After:
+```js
+connectedCallback() {
+  super.connectedCallback();
+  if (!isServer) {
+    this.items = this.querySelectorAll('my-item');
+  }
+}
+```
+