Add BertForSequenceClassification with Native and WASM Examples

[sondalex]

This pull request introduces the BertForSequenceClassification model. It includes two examples to demonstrate its functionality:

• A native implementation example.
• A WebAssembly (WASM) example, which also supports ModernBert.

Additionally, the following type adjustments have been made to align with common conventions observed in Hugging Face models:

• label2id: Updated to use a string key and an unsigned integer value, reflecting common Hugging Face model configurations.
• id2label: Modified in DebertaV2 to use a string key and a string value, consistent with Hugging Face model configurations

Note: The WASM example depends on methods not yet available in the main branch of the upstream tokenizers repository. It is compatible with changes proposed in https://github.com/huggingface/tokenizers/pull/1758