Proguard rules

[c3zius]

For using this library with proguard you need to put this rule:
-keep class com.bumptech.glide.gifdecoder.** { *; }
in your proguard-rules file.
I think this information need to add in project readme file.

[Mouadabdelghafouraitali]

@c3zius thank you so much bro!!