Add the `modernbert` tag

Hello!

## Pull Request overview
* Add the `modernbert` tag

## Details
If a model uses the `transformers` library_name, then the architecture is automatically taken from the `config.json` file and added as a tag, allowing people to easily search for models for a specific architecture ([example](https://huggingface.co/models?other=modernbert)). For GLiNER, this is understandably not done (it has different config files!), so this PR adds the architecture as a tag manually.

- Tom Aarsen

README.md

@@ -14,6 +14,7 @@ tags:
 - information extraction
 - encoder
 - entity recognition
+- modernbert
 base_model:
 - answerdotai/ModernBERT-base
 - BAAI/bge-small-en-v1.5