Feat: Add flag aliases feature

[oNaiPs]

@SupImDos first of all, thanks for such a useful project!

This PR attempts to implement #44.
It seems to have the functionality, however I'd like your guidance regarding next steps:

• What do you think of the implementation approach?
• Docs
• More Tests

Some comments regarding these edge cases:

What happens if you provide alias and aliases?
What is the behaviour for boolean arguments
What is the behaviour for inverted arguments (i.e., --no-<x>)

It seems to me that alias and aliases target different cases. Since alias maps to argparse's dest field, the optional aliases flags you set up would not alter this behavior.
In regards to the boolean option, BooleanOptionalAction should take care of it (if option starts with --, negates)
Finally, regarding inverted arguments, not sure what would be the case here, could you give an example?

Closes #44.

[oNaiPs]

Ping @SupImDos any chance you could look at this?

[SupImDos]

Ping @SupImDos any chance you could look at this?

Hi @oNaiPs, somehow I didn't see this! This looks great, I'll have a look at getting it merged and released ASAP.

[SupImDos]

@oNaiPs

What do you think of the implementation approach?

Looks great, this is pretty much how I was thinking it would be done.

Docs
More Tests

I think the easiest thing to do here is merge what you've got here into master, and I'll create a follow-up PR to address these. Hope that's okay!

[SupImDos]

@oNaiPs I did a bit of tweaking in #75 and released this feature in v0.10.0. Hope this is what you were looking for!

[oNaiPs]

@oNaiPs I did a bit of tweaking in #75 and released this feature in v0.10.0. Hope this is what you were looking for!

Thank you so much @SupImDos ! Yes most definitly!