Compat with built-in v-model transforms

[yyx990803]

Might want to add an actual mounted test suite to ensure consistent behavior with the built-in v-model - it's a bit more complicated than the current transforms. A few things come to mind:

• multi-checkbox binding for Arrays
• select and option binding
• component binding

One thing we need to do in addition to the event and domProps is adding a v-model runtime directive so code here can be leveraged.

[nickmessing]

@yyx990803, yeah, I've done it for now just as a POC, I'll check vue's code and will try to replicate same behaviour

[nickmessing]

@yyx990803, solved in 2.0.0

[yyx990803]

👍 thanks for the great job!