resolve
Returns the French spoken name for char, or null if TTS can handle it natively (a-z, 0-9).
Fallback chain:
Direct mapping (accents, symbols, punctuation)
Uppercase A-Z -> "X majuscule"
Lowercase a-z / digits 0-9 -> null (TTS say-as handles these)
Unmapped uppercase accent -> decompose from lowercase + "majuscule"
Unknown Unicode -> "caractere unicode code"
Return
The French spoken name, or null if the TTS engine handles it natively (a-z, 0-9).
Parameters
char
The character to resolve.