Fix ToolConfig type definition

```
export type BlockToolData = T;
export type ToolConfig = T;
```

suggestion:
```
export type BlockToolData = T | {};
export type ToolConfig = T | {};
```

Each tools should expect empty object as config.
When developing the tools, it is difficult to expect an error by empty object.

https://github.com/codex-team/editor.js/blob/next/src/components/modules/tools.ts#L345
https://github.com/codex-team/editor.js/blob/next/src/components/block/index.ts#L220