Fix chromium bug when calculating dynamic rows for text areas

#691

- Due to the width of the scrollbar, text areas change their inner width
under Chromium when the scrollbar is displayed. The use of offsetWidth
instead of contentRect ignores the presence of the scrollbar. The
calculation is therefore less accurate, but sufficient for estimating
the number of rows

docs/release-notes-common.md

 Allgemein
 =========
+## next
+### Fehlerbehebungen
+- Behebt "Flackern"-Fehler von Eingabebereichen mit dynamischen Zeilen unter Chromium
+
 ## editor/2.5.0+player/2.5.0
 ### Neue Funktion
 - Neues Element: Tabelle

projects/common/directives/dynamic-rows.directive.ts

 import {
-  AfterViewInit, ChangeDetectorRef, Directive, ElementRef, EventEmitter, Input, NgZone, OnChanges, Output, SimpleChanges
+  AfterViewInit,
+  ChangeDetectorRef,
+  Directive,
+  ElementRef,
+  EventEmitter,
+  Input,
+  NgZone,
+  OnChanges,
+  OnInit,
+  Output,
+  SimpleChanges
 } from '@angular/core';
 
 @Directive({
   selector: '[dynamicRows]'
 })
-export class DynamicRowsDirective implements AfterViewInit, OnChanges {
+export class DynamicRowsDirective implements OnInit, AfterViewInit, OnChanges {
   @Input() fontSize!: number;
   @Input() expectedCharactersCount!: number;
   @Output() dynamicRowsChange: EventEmitter<number> = new EventEmitter<number>();
@@ -20,9 +30,9 @@ export class DynamicRowsDirective implements AfterViewInit, OnChanges {
   ) {}
 
   ngOnInit(): void {
-    this.observer = new ResizeObserver(entries => {
+    this.observer = new ResizeObserver(() => {
       this.zone.run(() => {
-        this.width = (entries[0].contentRect.width);
+        this.width = this.elementRef.nativeElement.offsetWidth;
         this.calculateDynamicRows();
       });
     });