Add --ignore-case option

[davc0n]

ref. #101

[antonmedv]

Why is it needed?

[davc0n]

It's easier to find stuff if you have a folder with mixed files naming, some starting with capital letter, some not.
The default behavior puts all capital letters before the rest.

You said few time ago in this issue #101 that we could add such option.
If there's a better way to implement this, feel free to suggest ofc.

[davc0n]

@antonmedv Any update on this? What do you think?