feat: make callback return value optional in forEachBlock (#1081)

Author: m-risto

docs/pages/docs/editor-api/manipulating-blocks.mdx

@@ -91,7 +91,7 @@ Use `forEachBlock` to traverse all blocks in the editor depth-first, and execute
 
 ```typescript
 forEachBlock(
-  callback: (block: Block) => boolean,
+  callback: (block: Block) => boolean | undefined,
   reverse: boolean = false
 ): void;
 

packages/core/src/editor/BlockNoteEditor.ts

@@ -561,7 +561,7 @@ export class BlockNoteEditor<
       blockArray: Block<BSchema, ISchema, SSchema>[]
     ): boolean {
       for (const block of blockArray) {
-        if (!callback(block)) {
+        if (callback(block) === false) {
           return false;
         }