Allow user to pass filename for saving side runner output results

[harshitpeer-ekahal]

🚀 Feature Proposal

Allow the user to provide a filename as well, which can be used to save results with file name provided in the command

Motivation

While running multiple tests simultaneously, saving the results with specific filenames helps us to identify the results file better.

Example

selenium-side-runner --output-directory=results --output-file=website1
# Outputs results in `jest` format in `./results/website1.json'