Add activityIndicator prop support

[VincentCATILLON]

Description

This PR adds custom activity indicator override to be able to use a custom spinner instead of the default one provided by React Native.

It also fixes #79.

Result and observation

You should be able to use your custom loader (a Text component in Example folder)

iOS:

Android:

How to test?

Use Button.js example which provides the new prop

[VincentCATILLON]

@alvaromb Can you take a look at my PR ? :)

[VincentCATILLON]

@alvaromb ?

[VincentCATILLON]

ping @aaloy @alvaromb @amgxv @avallbona @bcanyelles @bercab @bmiro @celdrake @CrisHernandez @csalom @eduherraiz @francescarpi @franm @masterdreams @mgalofre @moreno97 @morenosan @paurullan @ponsperello90 @sastred @SoniaAG @tolorr @xusy2k

[a-morenovalls]

Hey @VincentCATILLON thanks for your PR, I will take a look, but please it's not necessary to mention all APSL team ;)

[SeanningTatum]

Wondering when this is going to be merged, all my jest tests are broken now after installing the library.

[VincentCATILLON]

3y after, nobody took a look. I'm closing it