Google added support for a lot of new tags and features

[lenaschimmel]

During 2021, Google introduces some new features:

• <phoneme>: Customize the pronunciation of specific words.
• <say-as interpret-as="duration">: Specify durations.
• <voice>: Switch between voices in the same request.
• <lang>: Use multiple languages in the same request.
• <mark>: Return the timepoint of a specified point in your transcript.

(it seems that ssml-check-core already supports <say-as interpret-as="duration"> and <mark> just fine)

The solution I'd like: ssml-check-core should probably support them in the same way the well-established tags are supported.

Describe alternatives you've considered If some or all of those features are not supported, the documentation should state this.

Additional context At first, those features were in beta phase (see this archived page) but I think they are out of beta now. I'm unsure if/how this relates to Google's v1 and v1beta1 APIs.

From my (limited) experience, the <phoneme> implementation is very picky and hard to debug, since every locale only supports a subset of the IPA phones, and the <phoneme> tag is completely ignored as soon as there's just one unsupported character in the ph attribute. The validation of ph would be a very useful feature, but also very complex. Maybe this should be a separate issue, or even be outsourced to a separate library?

[var1ap]

@gsdriver, can you please take a look?

[gsdriver]

Created a new issue for the ph attribute verification. The other items noted (supporting phoneme, voice, and lang) have been added into version 0.3.8