ENH: implement AliSim

[GavinHuttley]

• generates a single alignment
• supports the current substitution models (via name)
• takes a single tree
• supports rand seed
• supports alignment length
• supports insertion_rate, deletion_rate (the --indel cli parameter)
• extend_insert_name, extend_deletion_name (default to Zipfian)
• extend_param, delete_param

[rmcar17]

def ali_sim(tree: PhyloNode, 
            model: Model | str, 
            length: int, 
            *,
            seed: int | None, 
            insertion_rate: float = 0, 
            deletion_rate: float = 0, 
            insertion_size: IndelDistrubution | str = Zipfian(1.7,100),
            deletion_size: IndelDistribution | str = Zipfian(1.7,100),
) -> Alignment

Where IndelDistribution is a parent class of Zipfian, NegativeBinomial, Geometric, etc. - each taking their respective parameters in their inits.

[bqminh]

@trongnhanuit just created #200. I have an intern just started here ~1 month ago to work on that. Probably we should merge two feature requests together. If you did any code for ali_sim already, pls let us know.

[rmcar17]

Goodo! This issue has moreso been a wishlist item, so no code for ali_sim yet. Will hold off on merging until I have a better idea of the intended scope