chore: merge blocksuite source code (#9213)

blocksuite/blocks/src/database-block/context/host-context.ts

@@ -0,0 +1,7 @@
+import type { EditorHost } from '@blocksuite/block-std';
+import { createContextKey } from '@blocksuite/data-view';
+
+export const HostContextKey = createContextKey<EditorHost | undefined>(
+  'editor-host',
+  undefined
+);