Update function schema http://json.schemastore.org/function

#### What problem would the feature you're requesting solve? Please describe.
I want [CosmosDB](https://docs.microsoft.com/en-us/azure/azure-functions/functions-bindings-cosmosdb-v2) and other bindings to show up in editors.

#### Describe the solution you'd like
Update function schema: http://json.schemastore.org/function

#### Describe alternatives you've considered
Reading the docs myself? pshhhh

#### Additional context
Not a huge deal but it would be great

Start with the function schema at http://json.schemastore.org/function and compare it with the CosmosDB binding documentation linked in the issue. Done means the schema includes CosmosDB and other requested bindings so editors can display them.

Written by the indexing model from the issue text.