Adding Zalo as a messaging channel

[hiensarahly]

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...] --> Nope.

Describe the solution you'd like
A clear and concise description of what you want to happen. --> Integrate Zalo to the mix. Heavily used messaging app by individuals and businesses. Targeted in Vietnam.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[iammattmartin]

Any docs you can provide?

[QuickSales]

https://developers.zalo.me/docs