Add submarine cable example

[ditatompel]

Hey, thank you for creating an maintaining Numbat!

I made an example script that estimate the one-way and round-trip latency for data traveling through submarine cable. It's designed to be educational and demonstrates some numbat built-in functions and constant (c) for Network operators and new users who may not be very fluent in programming logic.

Although does not include highly variable or complex factors, such as latency from Dispersion Compensating Fiber (DCF), bufferbloat, and specific path chosen by dynamic routing protocols; the script produces a reasonable approximation for human and holds up well against real-world measurements (around ~3-5 ms in different when using the cable length between data centers in Singapore and Jakarta).

References:

https://www.submarinecablemap.com/submarine-cable/matrix-cable-system
https://www.m2optics.com/blog/bid/70587/calculating-optical-fiber-latency
https://mapyourtech.com/latency-in-optical-networks-principles-optimization-and-applications/

Thank you for your time and for considering this PR, I am open to any feedback or suggested changes.

[Goju-Ryu]

This looks really good, thank you for the contribution. I see that one check is failing, but I’m fairly certain it is unrelated to your PR. When I’m able, I will look into it so the last check can succeed before merging.