tag_resolver.transformer doesn't work anymore

[InakiAbete-Reflektion]

I think the issue was introduced here: cd529e7

Specifically here:
cd529e7#diff-e59af5a2ad8b55a0f76eb5218903478914a16f8a41a9136324406d442edaabb1R151-R158

Since tagTransfomers is initialized as undefined, !Array.isArray(tagTransfomers) will always return true.

Probably this could fix it, but I'm not sure:

// check if a transformer, legacy handling, transform single value input to array
    let tagTransfomers: Transformer[] | undefined = undefined
    if (Array.isArray(tagResolver.transformer)) {
      tagTransfomers = tagResolver.transformer as Transformer[]
    } else if (tagResolver.transformer !== undefined) {
      tagTransfomers = [tagResolver.transformer]
    }

[mikepenz]

Thank you for the report, will investigate this and fix prior to the final release of v4