Implement quota insertion

[Splat]

engine/modifiers/quoteinsert/quote_insertion.go needs to implement while matching to https://github.com/wietze/ArgFuscator.net/blob/main/src/Modifiers/QuoteInsertion.ts

Steps:

1. Unmarshal cfg into a Config struct.
2. Parse Config.Probability.
3. For each eligible token:
   a. Roll rand.Float64(); if >= probability, leave token unchanged.
   b. Pick a random insertion position between 1 and len(runes)- 1 (avoid position 0 or end to keep the token visually meaningful).
   c. Pick a quote character at random: " or '.
   d. Insert "" (or ”) at the chosen position.
4. Return updated tokens.