Picklist "editableOptions" has to be capitalized

[lucaslra]

Environment

azure-pipelines-task-lib version:

Issue Description

In the tasks.schema.json file, what is documented as "editableOptions": "True" actually must be "EditableOptions": "True", with capitalized E at the beginning

Expected behaviour

Picklist value can be edited manually

Actual behaviour

Picklist value canNOT be edited manually if used as documented on the schema file

Steps to reproduce

1. Create a new Extension contribution with a picklist field
2. Set options to "editableOptions": "True"
3. Picklist field will have incorrect behavior

[damccorm]

Fixed by #608