Block randomization algorithm as function

[kamilsi]

Permuted Block Randomization (PBR) is a widely used technique in clinical trials to ensure balanced allocation of participants across treatment arms while maintaining the random nature of assignment. The randomizeR package offers a robust foundation for PBR, but our project requires a more dynamic approach. We aim to implement a PBR algorithm that does not rely on a fixed number of randomization codes. Instead, it will generate blocks "just in time" as they are needed, offering flexibility and integration with our existing API. This approach will also allow for the modification of randomization settings, such as block sizes, during the study.

The goal of this task is to create just the function within the package + test coverage. Look at randomizeR tests, they look nice.