lint: make Props types readonly (step 2 of 3)

Make more Props types readonly.  In particular, the type `{}` is not
readonly, but the type `{||}` is.

This is also an automatic transformation, performed by the following:

  find src -name '*.js' |\
    xargs perl -i -0pe 's/PureComponent<\{\}>/PureComponent<\{||\}>/sg'

src/common/LineSeparator.js

@@ -5,7 +5,7 @@ import { View } from 'react-native';
 import type { ThemeColors } from '../styles';
 import { ThemeContext } from '../styles';
 
-export default class LineSeparator extends PureComponent<{}> {
+export default class LineSeparator extends PureComponent<{||}> {
   static contextType = ThemeContext;
   context: ThemeColors;
 

src/common/OptionDivider.js

@@ -5,7 +5,7 @@ import { View } from 'react-native';
 import type { ThemeColors } from '../styles';
 import { ThemeContext } from '../styles';
 
-export default class OptionDivider extends PureComponent<{}> {
+export default class OptionDivider extends PureComponent<{||}> {
   static contextType = ThemeContext;
   context: ThemeColors;
 

src/common/SectionSeparator.js

@@ -10,7 +10,7 @@ const styles = StyleSheet.create({
   },
 });
 
-export default class SectionSeparator extends PureComponent<{}> {
+export default class SectionSeparator extends PureComponent<{||}> {
   render() {
     return <View style={styles.separator} />;
   }

src/diagnostics/TimingScreen.js

@@ -6,7 +6,7 @@ import { Screen } from '../common';
 import TimeItem from './TimeItem';
 import timing from '../utils/timing';
 
-export default class TimingScreen extends PureComponent<{}> {
+export default class TimingScreen extends PureComponent<{||}> {
   render() {
     return (
       <Screen title="Timing" scrollEnabled={false}>

src/diagnostics/VariablesScreen.js

@@ -6,7 +6,7 @@ import config from '../config';
 import { Screen } from '../common';
 import InfoItem from './InfoItem';
 
-export default class VariablesScreen extends PureComponent<{}> {
+export default class VariablesScreen extends PureComponent<{||}> {
   render() {
     const variables = {
       enableReduxLogging: config.enableReduxLogging,

src/main/MainScreenWithTabs.js

@@ -7,7 +7,7 @@ import { OfflineNotice, ZulipStatusBar } from '../common';
 import MainTabs from './MainTabs';
 import styles from '../styles';
 
-export default class MainScreenWithTabs extends PureComponent<{}> {
+export default class MainScreenWithTabs extends PureComponent<{||}> {
   context: Context;
 
   static contextTypes = {

src/message/AnnouncementOnly.js

@@ -5,7 +5,7 @@ import { View } from 'react-native';
 import { Label } from '../common';
 import styles from '../styles';
 
-class AnnouncementOnly extends PureComponent<{}> {
+class AnnouncementOnly extends PureComponent<{||}> {
   render() {
     return (
       <View style={styles.disabledComposeBox}>

src/start/CompatibilityScreen.js

@@ -44,7 +44,7 @@ const GooglePlayBadge = () => (
   <Image style={styles.googlePlayBadge} source={googlePlayBadgePNG} resizeMode="contain" />
 );
 
-export default class CompatibilityScreen extends PureComponent<{}> {
+export default class CompatibilityScreen extends PureComponent<{||}> {
   storeURL =
     Platform.OS === 'ios'
       ? 'https://itunes.apple.com/app/zulip/id1203036395'

src/start/LoadingScreen.js

@@ -14,7 +14,7 @@ const styles = StyleSheet.create({
   },
 });
 
-export default class LoadingScreen extends PureComponent<{}> {
+export default class LoadingScreen extends PureComponent<{||}> {
   render() {
     return (
       <View style={styles.center}>

src/start/WelcomeHelpScreen.js

@@ -10,7 +10,7 @@ const styles = StyleSheet.create({
   },
 });
 
-export default class WelcomeHelpScreen extends PureComponent<{}> {
+export default class WelcomeHelpScreen extends PureComponent<{||}> {
   render() {
     return (
       <Screen title="Help" centerContent padding>