[question] Support for const?

**Describe the bug**
I am not sure if this is a feature request or a bug. I am trying to pass constant strings from the schema into the JSON output of the form. According to the JSON Schema spec this should be possible by using the "const" keyword. Unfortunately, I cannot get this to work with JSON Forms.

**To Reproduce**
Steps to reproduce the behavior:
1. Create a schema with the const keyword
2. Use it with the "seed" app
4. The element is ignored, i.e. not shown in the form nor output to the JSON data

**Expected behavior**
The constant data is passed through from the schema into the output.

**Browser (please complete the following information):**
Chrome

**Used Setup (please complete the following information):**
- Seed app from github repository

**Additional context**
I am trying to use JSON Forms to generate valid FHIR healthcare resource output.