Add Chinese localization

Addresses https://github.com/paperless-ngx/paperless-ngx/issues/134#issuecomment-1062950795

src-ui/angular.json

@@ -31,7 +31,8 @@
 					"ro-RO": "src/locale/messages.ro_RO.xlf",
 					"ru-RU": "src/locale/messages.ru_RU.xlf",
 					"sl-SI": "src/locale/messages.sl_SI.xlf",
-					"sv-SE": "src/locale/messages.sv_SE.xlf"
+					"sv-SE": "src/locale/messages.sv_SE.xlf",
+					"zh-CN": "src/locale/messages.zh_CN.xlf"
         }
 			},
 			"architect": {

src-ui/src/app/app.module.ts

@@ -1,6 +1,5 @@
 import { BrowserModule } from '@angular/platform-browser'
 import { NgModule } from '@angular/core'
-
 import { AppRoutingModule } from './app-routing.module'
 import { AppComponent } from './app.component'
 import {
@@ -84,6 +83,7 @@ import localeRo from '@angular/common/locales/ro'
 import localeRu from '@angular/common/locales/ru'
 import localeSl from '@angular/common/locales/sl'
 import localeSv from '@angular/common/locales/sv'
+import localeZh from '@angular/common/locales/zh'
 
 registerLocaleData(localeCs)
 registerLocaleData(localeDa)
@@ -101,6 +101,7 @@ registerLocaleData(localeRo)
 registerLocaleData(localeRu)
 registerLocaleData(localeSl)
 registerLocaleData(localeSv)
+registerLocaleData(localeZh)
 
 @NgModule({
   declarations: [

src-ui/src/app/services/settings.service.ts

@@ -264,6 +264,12 @@ export class SettingsService {
         englishName: 'Swedish',
         dateInputFormat: 'yyyy-mm-dd',
       },
+      {
+        code: "zh-cn",
+        name: $localize`Chinese Simplified`,
+        englishName: "Chinese Simplified",
+        dateInputFormat: "yyyy-mm-dd"
+      }
     ]
 
     // Sort languages by localized name at runtime