changesets: changeset for blueprint param overrides

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

.changeset/large-plants-rhyme.md

@@ -0,0 +1,30 @@
+---
+'@backstage/frontend-plugin-api': patch
+---
+
+It is now possible to override the blueprint parameters when overriding an extension created from a blueprint:
+
+```ts
+const myExtension = MyBlueprint.make({
+  params: {
+    myParam: 'myDefault',
+  },
+});
+
+const myOverride = myExtension.override({
+  params: {
+    myParam: 'myOverride',
+  },
+});
+const myFactoryOverride = myExtension.override({
+  factory(origFactory) {
+    return origFactory({
+      params: {
+        myParam: 'myOverride',
+      },
+    });
+  },
+});
+```
+
+The provided parameters will be merged with the original parameters of the extension.