More augmentation capabilities.

[yoavkatz]

We have a request for another augmentor that adds whitespace at both the start and end of string:

"let's add up to 5 consecutive whitespaces at the beginning and end of the prompt. Within the 5 slots, for each slot, pick between

{ " " : 20, "\t" : 10, "\n" : 40, "" : 30, }

It's simpler to AugmentSuffix, except that it's also for prefix as well + the selection is repeated 5 times .

Maybe we can generalize AugmentSuffix.