fix: export updateBlock, to allow extending heading block (#1235)

Author: m-risto

packages/core/src/index.ts

@@ -46,6 +46,7 @@ export * from "./util/string.js";
 export * from "./util/typescript.js";
 export { UnreachableCaseError, assertEmpty } from "./util/typescript.js";
 export { locales };
+export * from "./api/blockManipulation/commands/updateBlock/updateBlock.js";
 
 // for testing from react (TODO: move):
 export * from "./api/nodeConversions/blockToNode.js";