Add a design system (#34)

* Add theming system

* Add standard Button control and update RadioButtons

* Unify radiobutton with design system

* Update debug screen to have multiple views

* Add ToggleButton

* Update error controls to use design system

* Add typography to <Text> element

* Move DropdownButton into the design system

* Clean out old code

* Move Text into design system

* Add 'inverted' color palette

* Move LoadingPlaceholder into the design system

src/view/com/onboard/FeatureExplainer.tsx

@@ -10,7 +10,7 @@ import {
 } from 'react-native'
 import {TabView, SceneMap, Route, TabBarProps} from 'react-native-tab-view'
 import {FontAwesomeIcon} from '@fortawesome/react-native-fontawesome'
-import {Text} from '../util/Text'
+import {Text} from '../util/text/Text'
 import {UserGroupIcon} from '../../lib/icons'
 import {useStores} from '../../../state'
 import {s} from '../../lib/styles'

src/view/com/onboard/Follows.tsx

@@ -2,7 +2,7 @@ import React from 'react'
 import {SafeAreaView, StyleSheet, TouchableOpacity, View} from 'react-native'
 import {observer} from 'mobx-react-lite'
 import {SuggestedFollows} from '../discover/SuggestedFollows'
-import {Text} from '../util/Text'
+import {Text} from '../util/text/Text'
 import {useStores} from '../../../state'
 import {s} from '../../lib/styles'