I don't think anyone's done a plugin for that. As far as I know most people use apps outside VaM, then add the voice lines to Scene Audio and play from the character's HeadAudioSource with a trigger.
Here's an example guide using Microsoft Azure.
Don't you wish VAM had more story based content? I think the major thing holding this back is the lack of voice. Are you sick of using speech bubbles in VAM? Don't you wish there was an easy way to generate excellent TTS (text to speech) that...
hub.virtamate.com
I use rvc-tts-webui since it let's you use RVC models that you can get from places like
weights.gg. Might be a little more hard to setup though.
Text-to-Speech Gradio webui using RVC and edge-tts - litagin02/rvc-tts-webui
github.com
Edit: You can also make voice lines on
weights.gg and download those. Not sure if there are any limitations.