Feature request: Custom BLAKE2b size

**Is your feature request related to a problem? Please describe.**
Blake2b allow custom digest size between 1 - 64 bytes (8-512 bits). The UI only allow 128, 160, 256, 384, 512 bits to be selected.

**Describe the solution you'd like**
The digest size should be a free text field instead of drop down. This should also apply to Blake2s

**Describe alternatives you've considered**
Changing the digest size in URL also doesn't work