resolver - _meta.block.number

Hi,

is it possible to extend a graphql type with a block number of the block-tracking-plugin?
e.g. ...

```
extend type Lock {
      blockNumber: Int! @resolveTo(
        sourceName: "unlock"
        sourceTypeName: "Query",
        sourceFieldName: "_meta",
        requiredSelectionSet: "{ block { number } }",
        sourceArgs: {}
     )
}
```

Thanks :)