Optimize Deduplication for add_single_items Method

[ayush-vibrant]

When using the add_single_items method for bulk additions, there's potential for optimization.

• Issue: Currently, items in a batch are treated in isolation, leading to potential redundant similarity checks when the batch itself contains similar items.

• Suggestion: Before comparing items in the batch with the main list, check for and handle similarities within the batch itself. This can streamline the deduplication process and reduce computational overhead, especially for batches with duplicate or closely similar items.

By addressing this, we can enhance the efficiency of the deduplication process for bulk item additions.

PS: I've read the disclaimer in the README, but I believe the aforementioned optimization could be a minor enhancement that may yield significant improvements.