Include others shortener providers

[Owanesh]

Hello, before read this issue let me explain what is the idea behind this repo.
I started this repo only to try a new programming language, I choose nim (obvly) but I learned it as standalone, and as you can see I have a lot of to learn to improve my code.
Since I'm a curious developer I'm interested to know what are best practices and how I can improve this code, maybe with tests or a plugin based system...

Are or have you used Nim for you personal/work project?
Help me to know more :)

Include others shortener providers

I'd like to have more providers availables
My dream is to have Bit.ly avaiable maybe to use with extra parameters for apikey, or use a custom dotfile with credentials/preferences*. (Bit.ly isn't a must, you can implement whoever you want or maybe implement what you use daily)

* Idea of dotfile is a good point to set preferences like preferred provider and/or apikeys/passwords

Can you help me?
Feel free to change structure of provider and it's detect system, I chose a simple implementation but maybe is not good enough :/

Happy #hacktoberfest

Do you prefer another issue for "improve provider detect system and plugin based system"?
Rate this issue with a 🚀 and I will open it :)