(optim): debounce the search input handler

- so it doesn't fire for every character and have lagging output,
  debounce it for a better user experience and less wasteful
  network activity
  - also fixes some consistency errors that happen when requests
    finish out-of-order, like when you backspace out completely but
    there are still some manga showing

- tried to do it in the MST action initially, but this caused MST
  flow errors, so did it in the view instead
  - and, on second thought, that makes more sense, as the action
    could be used outside of this UI interaction and probably
    shouldn't be so closely coupled to it

- (deps): add lodash.debounce to handle this

components/mainView.js

@@ -1,6 +1,7 @@
 import React from 'react'
 import { StatusBar, View, Text, TextInput, SectionList } from 'react-native'
 import { inject, observer } from 'mobx-react'
+import debounce from 'lodash.debounce'
 
 import MangaList from './mangaList.js'
 import PageList from './pageList.js'
@@ -42,7 +43,7 @@ export default class MainView extends React.Component {
         sections={[
           {
             title: 'Search...',
-            props: { onChangeText: submitQuery },
+            props: { onChangeText: debounce(submitQuery, 200) },
             data: [{ mangas: searched, onSelect: selectManga }]
           },
           {

package.json

@@ -14,6 +14,7 @@
   "dependencies": {
     "cheerio-without-node-native": "^0.20.2",
     "expo": "^33.0.0",
+    "lodash.debounce": "^4.0.8",
     "mobx": "^5.9.4",
     "mobx-react": "^5.2.5",
     "mobx-state-tree": "^3.14.0",