Dynamically update json env

[1000thSummer]

Is your feature request related to a problem? Please describe.
We would like to dynamically update json files during the MTP rendering process.
There are 2 approaches at this moment but not fit our requirement very well:

• overrideStrategy: merge

This approach requires 2 json object pre-defined in upper-level config-map, which sometimes we don't have.

• using handlerbars helper function assign

This approach will assign values to a json object, BUT under a nested path `data.root`
https://github.com/razee-io/MustacheTemplate/blob/master/src/handlebar-helpers.js#L12

Describe the solution you'd like
A more straight-forward helper function would be ideal, and can be as simple as

  assign: function (obj, key, value) {
    if (!obj) {
      obj = {};
    }
    obj[key] = value;
  },

Describe alternatives you've considered
allowing dynamically adding helper function during rendering would also be great and allow more flexibility.

Additional context
N/A

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.