Added docs and removed an unused import.

src/app/common/components/avatar/avatar.ts

-import { Component, EventEmitter, ChangeDetectorRef } from '@angular/core';
+import { Component, EventEmitter } from '@angular/core';
 import { UserAvatarService } from '../../services/user-avatar.service';
 import { of, Observable } from 'rxjs';
 

src/app/common/services/user-avatar.service.ts

+/**
+ * @author Ben Hayward
+ * @desc Singleton service used to store the current user avatar as a BehaviorSubject.
+ */
 import { Injectable } from '@angular/core';
 import { BehaviorSubject } from 'rxjs';
 
-// Singleton
 @Injectable({
   providedIn: 'root',
 })