feat: Custom Dictionary for Cantonese phonemizer

[Aldof101]

This PR adds custom dictionary functionality similar to the Chinese CVV (October) phonemizer. The phonemizer now loads YAML dictionary files (zhyue.yaml) from singer and plugin folders, allowing users to define custom phoneme splits while maintaining backward compatibility with built-in rules.

[Aldof101]

I've included an example custom zhyue.yaml file, formatted similarly to the zhcvv.yaml file of the Chinese CVV phonemizer (refer to #776). Since the Cantonese Syo phonemizer retains the interface for automatically mapping Chinese characters to Jyutping, users can now directly input Chinese characters and they will be automatically converted to Jyutping and then split according to the custom dictionary rules.
zhyue.yaml