UI infrastructure and simple "Help" dialog (#3)

Sets up some WIP infrastructure for building out the UI, and adds a simple popup
to show the navigation controls for the app.

studio-frontend/src/app/help.element.ts

@@ -0,0 +1,49 @@
+import { LitElement, html, unsafeCSS } from "lit";
+import { customElement } from "lit/decorators.js";
+
+import styles from "./help.element.scss?inline";
+
+@customElement("sts-help")
+export class HelpElement extends LitElement {
+	static override styles = unsafeCSS(styles);
+
+	protected override render = () => html`
+		<table>
+			<thead>
+				<tr>
+					<th>Action</th>
+					<th>Controls</th>
+					<th>Alternate</th>
+				</tr>
+			</thead>
+			<tbody>
+				<tr>
+					<td>Pan view</td>
+					<td colspan="2">MMB</td>
+				</tr>
+				<tr>
+					<td>Orbit around point</td>
+					<td colspan="2">Alt + LMB</td>
+				</tr>
+				<tr>
+					<td>Zoom</td>
+					<td>Alt + RMB</td>
+					<td>Mouse Wheel</td>
+				</tr>
+				<tr>
+					<td>Free fly</td>
+					<td colspan="2">W, A, S, D</td>
+				</tr>
+				<tr>
+					<td style="padding-left: 20px">Up / Down</td>
+					<td colspan="2">E, Q</td>
+				</tr>
+				<tr>
+					<td>Free look</td>
+					<td>RMB</td>
+					<td>Shift</td>
+				</tr>
+			</tbody>
+		</table>
+	`;
+}