Fix .mocharc.js example in Mocha documentation

[fifle]

Hi everyone! I would like to introduce the fix for the page that describes the setup for the Mocha runner: https://allurereport.org/docs/mocha/#:~:text=In%20the%20script,for%20test%20results.

It includes an example for the .mocharc.js file, but it contains a mistake. I'm not sure if the reporterOptions parameter was supported before, but it's not working anymore. Mocha's documentation and samples refer to another parameter called 'reporter-option', which is actually an array.

Since I'm using .mocharc.js mainly to pass the environment value for Allure's resultsDir, I would recommend modifying the existing example to this one:

module.exports = {
    parallel: false,
    reporter: 'allure-mocha',
    'reporter-option': ['resultsDir=allure-results']
};

Alternatively, you could include an environment variable for the reporter-option array:

module.exports = {
    parallel: false,
    reporter: 'allure-mocha',
    'reporter-option': [`resultsDir=${process.env.ALLURE_RESULTS_DIR || 'allure-results'}`]
};