feat: implement channel groups view

src/app/material.module.ts

@@ -1,6 +1,7 @@
 import { NgModule } from '@angular/core';
 import { MatButtonModule } from '@angular/material/button';
 import { MatCardModule } from '@angular/material/card';
+import { MatExpansionModule } from '@angular/material/expansion';
 import { MatIconModule } from '@angular/material/icon';
 import { MatInputModule } from '@angular/material/input';
 import { MatListModule } from '@angular/material/list';
@@ -13,6 +14,7 @@ import { MatSnackBarModule } from '@angular/material/snack-bar';
     exports: [
         MatButtonModule,
         MatCardModule,
+        MatExpansionModule,
         MatIconModule,
         MatInputModule,
         MatListModule,