web: allow Sidebar to be opened on mobile (#417)

* web: initial sidebar trigger on mobile

* web: render hamburger button as overlay top right

web/src/elements/sidebar/SidebarHamburger.ts

@@ -0,0 +1,35 @@
+import { css, CSSResult, customElement, html, LitElement, TemplateResult } from "lit-element";
+import { COMMON_STYLES } from "../../common/styles";
+
+@customElement("ak-sidebar-hamburger")
+export class SidebarHamburger extends LitElement {
+
+    static get styles(): CSSResult[] {
+        return COMMON_STYLES.concat(
+            css`
+                :host {
+                    position: absolute;
+                    top: var(--pf-c-page__main-section--PaddingTop);
+                    right: var(--pf-c-page__main-section--PaddingRight);
+                    z-index: 250;
+                }
+            `
+        );
+    }
+
+    onClick(): void {
+        this.dispatchEvent(
+            new CustomEvent("ak-sidebar-toggle", {
+                bubbles: true,
+                composed: true,
+            })
+        );
+    }
+
+    render(): TemplateResult {
+        return html`<button @click=${() => (this.onClick())} class="pf-c-button pf-m-plain" type="button">
+            <i class="fas fa-bars" aria-hidden="true"></i>
+        </button>`;
+    }
+
+}