Discussion: add babel plugin vue jsx sync

[LucienLee]

Want to discuss about whether adding babel-plugin-vue-jsx-sync to preset.

This plugin enable sync modifier in JSX, which it's as useful as v-model. Since this preset has model plugin, I think sync could be added too.

[njleonzhang]

I make a PR, #8

[sant123]

@egoist ? May you review it? Please?

[egoist]

@sant123 that plugin is still young and might be buggy so we won't merge it for now. But you can already use it if you want, it's not necessary to be included in this preset.