Use of optimised kernels

By default, the script uses the unoptimised kernels, by adding -O to:
https://github.com/HashPals/Search-That-Hash/blob/d5f5f0fc39d506eb7a58c4f5da841d7b7cf51c00/search_that_hash/cracker/offline_mod/hashcat.py#L12
It should get an easy and free speed increase with the only draw back of a slightly reduced max plain length, typically from 255 to 32 characters
```
> hashcat -m 0 -w 4 -b --quiet
Hashmode: 0 - MD5

Speed.#1.........: 4996.0 MH/s (170.43ms) @ Accel:64 Loops:1024 Thr:1024 Vec:1

> hashcat -m 0 -w 4 -b --quiet -O
Hashmode: 0 - MD5

Speed.#1.........: 9154.5 MH/s (90.30ms) @ Accel:64 Loops:1024 Thr:1024 Vec:1
```