Merge branch 'tweak-frontpage' into 'master'

Tweak frontpage

See merge request arsnova/arsnova-lite!175

src/app/components/shared/room-join/room-join.component.html

 <div fxLayout="column" fxLayoutAlign="center center" fxlayoutgap="50px" fxFill>
 <form (ngSubmit)="joinRoom(roomId.value)">
   <div fxLayout="row" fxLayoutAlign="center" fxLayoutGap="10px">
-    <mat-form-field>
+    <mat-form-field (keyup.enter)="onEnter()">
       <input matInput #roomId type="text" pattern="[0-9 ]*" inputmode="numeric" min="00000000" max="99999999"
              onkeydown="if(this.value.length - (this.value.split(' ').length -1) === 8 && event.keyCode != 8) return false;
                         if(this.value.length === 4 && event.keyCode != 8) this.value = this.value + ' ';"

src/app/components/shared/room-join/room-join.component.ts

-import { Component, OnInit } from '@angular/core';
+import { Component, OnInit, ViewChild, ElementRef } from '@angular/core';
 import { Room } from '../../../models/room';
 import { RoomService } from '../../../services/http/room.service';
 import { Router } from '@angular/router';
@@ -24,6 +24,7 @@ export class JoinErrorStateMatcher implements ErrorStateMatcher {
   styleUrls: ['./room-join.component.scss']
 })
 export class RoomJoinComponent implements OnInit {
+  @ViewChild('roomId') roomIdElement: ElementRef;
 
   room: Room;
   demoId = '95680586';
@@ -41,9 +42,14 @@ export class RoomJoinComponent implements OnInit {
   }
 
   ngOnInit() {
+    this.roomIdElement.nativeElement.focus();
     this.authenticationService.watchUser.subscribe(newUser => this.user = newUser);
   }
 
+  onEnter() {
+    this.getRoom(this.roomIdElement.nativeElement.value);
+  }
+
   getRoom(id: string): void {
     if (id.length - (id.split(' ').length - 1) < 8) {
       this.translateService.get('home-page.exactly-8').subscribe(message => {