Model: Add TokenizerConfig stub and add_eos_token fallback

This stub fetches the add_eos_token field from the HF tokenizer config.
Ideally, this should be in the backend rather than tabby.

Signed-off-by: kingbri <8082010+kingbri1@users.noreply.github.com>

common/templating.py

@@ -239,6 +239,7 @@ async def find_prompt_template(template_name, model_dir: pathlib.Path):
         ]
 
     # Add lookup from prompt template name if provided
+    # TODO: Possibly link to the TokenizerConfig class
     if template_name:
         find_template_functions[:0] = [
             lambda: PromptTemplate.from_file(pathlib.Path("templates") / template_name),