[FR] - Support feature.only like Scenario.only

[kobenguyent]

Currently, in a test file, when we add .only to a Scenario like following, only that Scenario will be triggered.

Feature('My First Test');

Scenario.only('test something', ({ I }) => {
  I.amOnPage('https://github.com');
  I.see('GitHub');
});

Scenario('test something 2', ({ I }) => {
  I.amOnPage('https://github.com');
  I.see('GitHub');
});

Scenario('test something 3', ({ I }) => {
  I.amOnPage('https://github.com');
  I.see('GitHub');
});

We'd like to have Feature.only so that all scenarios of that Feature would be triggered, that would be very handy when we want to run a specific Feature.

Feature.only('My First Test');

Scenario('test something', ({ I }) => {
  I.amOnPage('https://github.com');
  I.see('GitHub');
});

Scenario('test something 2', ({ I }) => {
  I.amOnPage('https://github.com');
  I.see('GitHub');
});

Scenario('test something 3', ({ I }) => {
  I.amOnPage('https://github.com');
  I.see('GitHub');
});