update embedding v2 snake case

[winzamark123]

This pull request standardizes the naming convention for the embedding V2 method across the codebase by renaming embeddingV2 to embedding_v2. This change ensures consistency and clarity in both method definitions and usage.

Naming consistency improvements:

• Renamed the method embeddingV2 to embedding_v2 in the General class, including all overloads and the implementation, in src/general/index.ts.
• Updated the binding in the General class constructor to use the new embedding_v2 method name in src/general/index.ts.
• Changed the property name from embeddingV2 to embedding_v2 in the returned object of the JigsawStack function in src/core.ts.