Initial requires_strict setup

[mgale]

This PR adds a new attribute called requires_strict which by default mimics the requires behaviour but will fail if the values are empty strings and provides an option called limit_values which can function like an enum:

  task-example:
    requires_strict:
      vars: [VAR_ONE, VAR_THREE, VAR_TWO]
      limit_values:
        VAR_TWO:
          - "foo"
          - "bar"
          - "two"
    cmds:
      - echo '{{.VAR_TWO}}'

Examples can be seen here: https://github.com/go-task/task/pull/1370/files#diff-62762ddb42701438813445ff0303d0f357cfe2d0d6f38969c45224befb143ea4

[mgale]

It has been over a month and a half since I created this PR and I haven't heard anything. I also tried reaching out on discord a few times and got no response. I am closing this PR, if this is something the community is interested in the future just reach out.