feat(vitest/require-local-test-context-for-concurrent-snapshots): add rule

[Haberkamp]

What?

I added a new rule. It forces the use of the local Test Context in snapshot tests that run in parallel. For more background, see #311.

Why?

This change improves the developer experience. It tells the developer that the test will fail while writing it. Without this rule the developer will find that out when test runs.

Testing?

To test the new rule you can execute the unit test. Or you clone the repo, activate the rule and insert the code snippet below:

import { describe, expect, it } from 'vitest';

describe.concurrent('something', () => {
  it('should report', () => {
    expect(true).toMatchInlineSnapshot('1');
  });

  it('should not report', (context) => {
    context.expect(true).toMatchSnapshot();
  });
});

it.concurrent('should report', () => {
  expect(1).toMatchInlineSnapshot();
});

it('should not report', (context) => {
  context.expect(1).toMatchInlineSnapshot();
});

I added the most common test scenarios I could think of. Please feel free to suggest relevant test scenarios that you think are beneficial.

Anything Else?

Resolves #311

[veritem]

Thank you so much for your time! Great work!!!