Please implement phonetic spelling

[Cleversn]

Is your feature request related to a problem? Please describe.
No.
Describe the solution you'd like
Some synthesisers in other languages than English, for example IBMTTS in Brazilian Portuguese, have a kind of bug that makes difficult to distinguish between some vowels when spelling. Thus, we need phonetic spelling, i.e. speaking alpha for a, bravo for b, charlie for c, etc. Some clients like Orca and Fenrir implement this feature theirselves, but Speechd-el for example doesn't. Thus, speech-dispatcher should have it too.
Describe alternatives you've considered

Additional context

[sthibaul]

AIUI it would thus rather be per-module? This could probably be a parameter of the IBMTTS module? (and the implementation can be shared with other modules that would need it)