feat: Regex and environmental variable support added

[kidunot89]

Summary

• Replaces runFrom parameter with options parameter on the execute and spawn callbacks.

  const options: Partial<{
    runFrom: string, // where to execute command from.
    env: Record<string, unknown>, // environment variables to be set on the process when the command is executed
    timeout: number, // execute only
  }> | undefined = {};

  const { execute, spawn, cleanup } = await prepareEnvironment();
  
  const executeResult = await execute(
      'node',
      './test/testing-cli-entry.js env',
      { env: { HELLO: 'WORLD' } }
  );
  expect(executeResult).exitCodeToBe(0);
  expect(executeResult.stdout).toContain('- HELLO: WORLD');
  
  const { waitForText, waitForFinish } = await spawn(
      'node',
      './test/testing-cli-entry.js env',
      { env: { HELLO: 'UNIVERSE', NODE_ENV: 'Yes' } }
  );
  
  expect(await waitForText('- HELLO: UNIVERSE')).toBeFoundInOutput();
  expect(await waitForText('- NODE_ENV: Yes')).toBeFoundInOutput();
  expect(await waitForFinish()).exitCodeToBe(0);
  
  await cleanup();

• useRegex added to the options parameter for waitForText for more sophisticated captures.
  Note: Expression must be passed as a string with escaped backslashes e.g. "\\d+ dogs, \\d+ cats, and \\d+ birds"

  const { spawn, cleanup } = await prepareEnvironment();
  
  const {
      waitForText,
      waitForFinish,
  } = await spawn('node', './test/testing-cli-entry.js random');
  
  expect(
      await waitForText('\\d+ dogs, \\d+ cats, and \\d+ birds', { useRegex: true })
  ).toBeFoundInOutput();

• README.md updated.