[ADF-3874] icon component (#4112)

* adf-icon component

* demo shell example page

* add docs

* integration with thumbnail service

lib/core/icon/icon.component.ts

@@ -0,0 +1,55 @@
+/*!
+ * @license
+ * Copyright 2016 Alfresco Software, Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {
+    Component,
+    Input,
+    ViewEncapsulation,
+    ChangeDetectionStrategy
+} from '@angular/core';
+import { ThumbnailService } from '../services/thumbnail.service';
+
+@Component({
+    selector: 'adf-icon',
+    templateUrl: './icon.component.html',
+    styleUrls: ['./icon.component.scss'],
+    encapsulation: ViewEncapsulation.None,
+    changeDetection: ChangeDetectionStrategy.OnPush,
+    host: { class: 'adf-icon' }
+})
+export class IconComponent {
+    private _value = '';
+    private _isCustom = false;
+
+    get value(): string {
+        return this._value;
+    }
+
+    @Input()
+    set value(value: string) {
+        this._value = value || 'settings';
+        this._isCustom =
+            this._value.includes(':') ||
+            this.thumbnailService.mimeTypeIcons[value];
+    }
+
+    get isCustom(): boolean {
+        return this._isCustom;
+    }
+
+    constructor(private thumbnailService: ThumbnailService) {}
+}