How to Provide Blob Output Binding Binary Data in Custom Handlers?

#### Is your question related to a specific version? If so, please specify:

v2.0.

#### What language does your question apply to? (e.g. C#, JavaScript, Java, All)

Custom Handler (Ballerina)

#### Question

While implementing a custom handler for the [Ballerina](https://github.com/lafernando/module-ballerinax-azure.functions) language, based on the documentation [here](https://docs.microsoft.com/en-us/azure/azure-functions/functions-custom-handlers), it doesn't mention how to provide a binary value to the JSON response we return in custom handlers. In a blob input handler, it does return a base64 encoded text where we can decode to get the binary data. But in the output case, it simply considers all the content given in the output JSON as simple text (not like base64 encoded data). Is there any special attribute or something we need to set in the output in order to provide a binary (base64 maybe) value?