Remove checking for valid images so other file extensions can be used

[janekkkk]

Solves #84

[devTam]

Can this be merged please? This feature is needed

[Jason-Weyland]

@janekkkk can we get this merged in? I'm running into issues that this would fix.

[vutoan266]

hi @janekkkk, thank you so much for your enthusiasm to make a good PR. It will work well for your case.
But after some consideration, I decide to continue to retain image checking logic, and will support one more prop allowNonImageType in version 3.1.7.
Anyway, the lib was born to solve image business, so I think the new prop will serve your demand and still keep the original purpose itself.
Again, thank you bro!

[vutoan266]

Hi @devTam and @Jason-Weyland you guys can try the new version 3.1.7. Feel free to connect with me if have any issues or concerns.