Editor: a React-free entry for the TipTap extensions, and custom block types in BlockEditor #62

javaabu/block-editor (Javaabu/block-editor#2) reuses Onu's TipTap pieces from @javaabu/onu/editor: ThaanaKeyboard, AutoDirection, CalloutNode and Embed, plus attachThaanaKeyboard from @javaabu/onu/thaana. Its editor UI is framework-free, so Blade apps can use it without React.

Two things would make that cleaner. Neither blocks block-editor; it works today.

1. A React-free entry for the TipTap extensions. @javaabu/onu/editor re-exports the React editors, so a Vite build that only uses ThaanaKeyboard still has to resolve react, @tiptap/react, @tiptap/static-renderer, radix-ui and the rest. They tree-shake out of the bundle, but Blade-only apps must install them. Something like @javaabu/onu/editor/extensions (ThaanaKeyboard, AutoDirection, CalloutNode, Embed, createSchemaExtensions, toEmbedUrl, isSafeUrl) and a React-free @javaabu/onu/thaana/core (keymaps, transliterate, attachThaanaKeyboard) would fix that.
2. Custom block types in BlockEditor's / and + menus (a blocks prop of BlockType[] rather than the closed BlockTypeId union). With that, a React-only app could use Onu's BlockEditor for simple custom blocks. block-editor keeps its own shell either way, because its blocks come from PHP config with settings panels.

detectDirection / resolveBlockDirection would also be handy exports. block-editor has its own copy, so its PHP renderer and React renderer agree.