feat: Add Image component

[iRoachie]

Implements #1478

Motivation

Adds Image component that has support for placeholders. Basically takes out the FadeInImage component that @martinezguillaume wrote in react-native-training/react-native-elements@f8af41c and splits it into it's own component.

A follow-up PR will let the Avatar component use this.

API

import { ActivityIndicator } from 'react-native';
import { Image } from 'react-native-elements';

// Standard Image
<Image
  source={{ uri: image }}
  style={{ width: 200, height: 200 }}
/>


// Image with custom placeholder content
<Image
  source={{ uri: image }}
  style={{ width: 200, height: 200 }}
  PlaceholderContent={<ActivityIndicator />}
/>

Screenshots

[codecov]

Codecov Report

Merging #1582 into next will increase coverage by 0.34%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##             next    #1582      +/-   ##
==========================================
+ Coverage   76.23%   76.58%   +0.34%     
==========================================
  Files          32       33       +1     
  Lines         606      615       +9     
  Branches       78       78              
==========================================
+ Hits          462      471       +9     
  Misses        125      125              
  Partials       19       19

Impacted Files	Coverage Δ
src/image/Image.js	100% <100%> (ø)

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