[ADF-1549] Added files for Core library (#2345)

* [ADF-1549] Added files for Core library

* [ADF-1549] Updated md files following checks

docs/accordion.component.md

@@ -0,0 +1,48 @@
+# Accordion Component
+
+Creates an accordion menu, optionally with a custom header and icon.
+
+<!-- markdown-toc start - Don't edit this section.  npm run toc to generate it-->
+
+<!-- toc -->
+
+- [Basic Usage](#basic-usage)
+  * [Properties](#properties)
+
+<!-- tocstop -->
+
+<!-- markdown-toc end -->
+
+## Basic Usage
+
+```html
+<adf-accordion>
+    <adf-accordion-group [heading]="titleHeading" [isSelected]="true" [headingIcon]="'assignment'">
+        <my-list></my-list>
+    </adf-accordion-group>
+</adf-accordion>
+```
+
+```ts
+@Component({
+    selector: 'my-component'
+})
+export class MyComponent implements OnInit {
+
+    titleHeading: string;
+
+    constructor() {
+        this.titleHeading = 'My Group';
+    }
+
+}
+```
+
+### Properties
+
+| Name | Type | Description |
+| --- | --- | --- |
+| heading | string | The header title. |
+| isSelected | boolean | Define if the accordion group is selected or not. |
+| headingIcon | string | The material design icon. |
+| hasAccordionIcon | boolean | Define if the accordion (expand) icon needs to be shown or not, the default value is true |