fix(package): adapted the src file to angular v8

Author: AnthonyNahas

src/module/components/ngx-material-pages/mat-page-content/mat-page-content.component.ts

@@ -9,7 +9,7 @@ import {ChangeDetectionStrategy, Component, Input, OnInit, TemplateRef, ViewChil
 export class MatPageContentComponent implements OnInit {
 
   /** Template for page content. */
-  @ViewChild(TemplateRef) content: TemplateRef<any>;
+  @ViewChild(TemplateRef, {static: false}) content: TemplateRef<any>;
 
   @Input()
   title: string;

src/module/components/ngx-material-pages/mat-page-loader/mat-page-loader.component.ts

@@ -9,7 +9,7 @@ import {MatPageContentComponent} from '../mat-page-content/mat-page-content.comp
 })
 export class MatPageLoaderComponent {
 
-  @ContentChild(MatPageOutlookComponent) pageOutlook: MatPageOutlookComponent;
-  @ContentChild(MatPageContentComponent) pageContent: MatPageContentComponent;
+  @ContentChild(MatPageOutlookComponent, {static: false}) pageOutlook: MatPageOutlookComponent;
+  @ContentChild(MatPageContentComponent, {static: false}) pageContent: MatPageContentComponent;
 
 }

src/module/components/ngx-material-pages/mat-page-outlook/mat-page-outlook.component.ts

@@ -22,7 +22,7 @@ import {
 export class MatPageOutlookComponent implements OnInit {
 
   /** Template for page outlook content. */
-  @ViewChild(TemplateRef) content: TemplateRef<any>;
+  @ViewChild(TemplateRef, {static: false}) content: TemplateRef<any>;
 
   @Input()
   title: string;

src/module/components/ngx-material-pages/mat-pages.component.ts

@@ -16,10 +16,10 @@ import {MatSidenav, MatTabGroup} from '@angular/material';
 })
 export class MatPagesComponent implements OnInit, AfterContentInit {
 
-  @ViewChild('sidenav')
+  @ViewChild('sidenav', {static: false})
   sidenav: MatSidenav;
 
-  @ViewChild(MatTabGroup, {read: ElementRef})
+  @ViewChild(MatTabGroup, {read: ElementRef, static: true})
   tabHeader: ElementRef;
 
   @ContentChildren(MatPageLoaderComponent)