Bug/semaphore lock

<!-- Congratulations! You've made it this far! Thanks for submitting a PR to Infinity! ## License & CLA By submitting this PR, I confirm that my contribution is made under the terms of the [MIT license](https://github.com/michaelfeil/infinity/blob/main/LICENSE). --> ## Related Issue <!-- If you are sure that a related issue should be automatically closed, use the syntax to close issue 123. closes #123 --> ## Checklist - [x] I have read the [CONTRIBUTING](https://github.com/michaelfeil/infinity/tree/main?tab=readme-ov-file#contribute-and-develop) guidelines. - [ ] I have added tests to cover my changes. - [x] I have updated the documentation (docs folder) accordingly. ## Additional Notes Hi! When running multiple jobs asynchronously, a semaphore lock occurs. Multiple jobs will increment the semaphore counter to >3, and after the first job completes, the lock will remain. I suggest using a mutex, so all new jobs will simply wait for it to be released and then proceed quietly. Example code with locking: ```python import uuid import asyncio from infinity_emb import AsyncEmbeddingEngine, EngineArgs async def run_job_a(engine: AsyncEmbeddingEngine, texts: list[str]) -> list[list[float]]: task_id = uuid.uuid4() print(f"{task_id=} started") async with engine: result, usage = await engine.embed(sentences=texts) print(f"{task_id=} completed") return result async def main() -> None: args = EngineArgs( model_name_or_path="/home/models/e5-small-v2", ) engine = AsyncEmbeddingEngine.from_args(engine_args=args) outputs = await asyncio.gather( run_job_a(engine=engine, texts=["a", "b", "c", "d"]), run_job_a(engine=engine, texts=["a", "b", "c", "d"]), run_job_a(engine=engine, texts=["a", "b", "c", "d"]) ) if __name__ == "__main__": asyncio.run(main()) ``` I understand that the behavior with constantly turning on/off the engine is incorrect, but suddenly someone wants to do this)