Request to add multithreading support

[supply9243]

I don't speak English, these are translated by software:

I've noticed that the software creates only one thread at a time and verifies a single file, then closes the thread.
We need to verify a large number of files, and the disk I/O consumed by verifying a single file is limited.
This approach does not fully utilize the performance of multi-core CPUs and SSDs (some of which can achieve speeds up to 12GB/s).
If you are concerned about affecting the HDD, you can make this an optional setting.

[OV2]

RapidCRC uses multiple threads, but only for calculating different hash types at the same time. You are correct that only one file is calculated at a time.
The current structure makes it difficult to change this, but it is on my todo.