Add support for project datatype in custom fields

[oveaurs]

#481

[ankitpokhrel]

Hi @oveaurs, I don't see this field format in the Jira doc. I am wondering what's the datatype for this field returned by the /field API?

[oveaurs]

    "id": "customfield_13467",
    "name": "Cross over project",
    "custom": true,
    "orderable": true,
    "navigable": true,
    "searchable": true,
    "clauseNames": [
      "cf[13467]",
      "Cross over project"
    ],
    "schema": {
      "type": "project",
      "custom": "com.atlassian.jira.plugin.system.customfieldtypes:project",
      "customId": 13467
    }
  },

I found a reference to that datatype here: https://developer.atlassian.com/cloud/jira/platform/rest/v2/api-group-issue-fields/

[ankitpokhrel]

I see, thank you for the reference. The changes looks OK to me.

[ankitpokhrel]

Thank you for your contribution 🎉