Improvements to the feature explainer, including intro screen and screenshot of scenes

src/view/lib/assets.native.ts

@@ -1,3 +1,4 @@
 import {ImageSourcePropType} from 'react-native'
 
 export const DEF_AVATAR: ImageSourcePropType = require('../../../public/img/default-avatar.jpg')
+export const SCENE_EXPLAINER: ImageSourcePropType = require('../../../public/img/scene-explainer.jpg')

src/view/lib/assets.ts

@@ -1,3 +1,6 @@
 import {ImageSourcePropType} from 'react-native'
 
 export const DEF_AVATAR: ImageSourcePropType = {uri: '/img/default-avatar.jpg'}
+export const SCENE_EXPLAINER: ImageSourcePropType = {
+  uri: '/img/scene-explainer.jpg',
+}