[REQ]RAR: Support for Dictionary Configuration

[A2Sumie]

Is your feature request related to a problem? Please describe

Keka w/ rar does not offer configuration for dictionary sizes. I process 32-bit float wav files frequently. A 1GB dictionary could provide about an additional 10% improvement in compression rates(~74%@ def. -> ~65%) for these files. And rar cli does provide a dictionary config flag.

Describe the solution you'd like

Let Keka support dictionary configs, like WinRAR does.

Describe alternatives you've considered

Use as-is. Default RAR5 settings is already superior than 7z and zstd for 32-bit floats. Using the rar command line. Not quite convenient though.

Additional context

Add any other context or screenshots about the feature request here.