stream.wasm : add language selection support (#3354)

stream.wasm : add language selection support (#3354)

* stream.wasm : add language selection support

This commit adds support for selecting the language in the stream.wasm
example. This is includes adding the model `base` which supports
multilingual transcription, and allowing the user to select a language
from a dropdown menu in the HTML interface.

The motivation for this is that it allows users to transcribe audio in
various languages.

Refs: https://github.com/ggml-org/whisper.cpp/issues/3347

* squash! stream.wasm : add language selection support

Remove strdup() for language in stream.wasm and update butten text for
base (should not be "base.en" but just "base").