L'Ambre metric

[sebastianGehrmann]

https://arxiv.org/abs/2103.16590

[jordiclive]

@sebastianGehrmann, I had a look at the author's repository: https://github.com/adithya7/lambre.

This metric is reference-less and source-less. This metric supports en, cs, de, es, ru. However, it requires downloading stanza parser and rules for each language. For each language, this is ~250Mb?

Happy to try and integrate, if you think this is ok.