Added new command to easily add json value into yaml file

[lstocchi]

PLEASE DON'T MERGE
This is a possible workaround to add json string into yaml file in azure devops. In this way user can add their json without worrying about double quotes escaping.
Possible solution for #35

[lstocchi]

This new command allows the user to add a json string to the yaml file and pass it to the ToolRunner without any issue or caring about double quotes escaping.

An example can be found below:

-task: oc-cmd-json@2
  inputs:
    openshiftService: 'My Openshift'
    version: 'v3.11.0'
    cmd: 'oc patch dc testwildfly -p=-json1'
    json: '{"-json1":{"spec":{"template":{"spec":{"containers":[{"name":"testwildfly","imagePullPolicy":"IfNotPresent"}]}}}}}'

In this case the string -json1 is replaced by using the value in the json object.
Currently there is no limitation in naming json keys.
The json object could have multiple key-value pairs.
The cmd string could have same json key repeated multiple times.

The only drawback that this PR doesn't solve is that the user need to use a specific syntax to deal with oc command arguments and json. By using the classic format (found in most oc tutorial)

'oc patch dc testwildfly -p -json1'

it will results in the following error

Error from server (BadRequest): json: cannot unmarshal string into Go value of type map[string]interface {}