Enhance CLI with Interactive Command-Based Arguments

[MahdiGraph]

Hello maintainers of speed-cloudflare-cli,

First and foremost, thank you for creating such a useful tool! I've been utilizing it extensively and I have a couple of feature requests that I believe would make the user experience even better.

Feature Requests:

1. JSON Output Mode: It would be immensely useful if there was an option to get the output in JSON format. This would make it easier to integrate with other tools or scripts, especially for those of us looking to automate or parse the results in different ways. A potential flag could be --json to enable this output mode. speed-cloudflare-cli --json

2. Selective Speed-Mode: While the comprehensive speed checks are great, sometimes we just want to get a quick check or are limited by data. It would be great to have command arguments to selectively check specific file sizes. Something like: speed-cloudflare-cli --speed-mode=25MB

This way, users can choose to only test certain sizes, saving time and bandwidth.

I believe these enhancements would make the tool even more flexible and user-friendly. I look forward to hearing your thoughts on these suggestions!

[hexmode]

JSON output has been resolved in #32.