Ability to set constants in pybtc.constants to support alt coins

[Lvl4Sword]

Describe the bug

Ability to easily set a lot of constants from pybtc.constants rather than having to go in and hardcode anything by editing pybtc/constants.py

To Reproduce
Steps to reproduce the behavior:

Self-explanatory from above

Additional context
Add any other context about the problem here.

No additional context needed

[4tochka]

Why did you classify it as a bug?

[Lvl4Sword]

Why did you classify it as a bug?

That's a good question, honestly. I don't think I saw the blank issue section initially.
Either way, #27 starts on this. Is there anything else needed to accept that PR?

[Lvl4Sword]

Circling back to this.
Is there anything that needs done for this?