Bugfix/context provider storybook (#699)

* move context-provider element to src/core to make it available to everything

* add extra documentation to the context-provider element

* fix imports from storybook

* import context-provider in app to make it globally available

* import umb-context-provider

src/Umbraco.Web.UI.Client/src/app.ts

@@ -5,6 +5,7 @@ import 'element-internals-polyfill';
 
 import './core/router/router-slot.element';
 import './core/router/variant-router-slot.element';
+import './core/context-provider/context-provider.element';
 
 import { UUIIconRegistryEssential } from '@umbraco-ui/uui';
 import { css, html } from 'lit';

src/Umbraco.Web.UI.Client/src/core/context-provider/context-provider.element.ts

@@ -2,12 +2,21 @@ import { html } from 'lit';
 import { customElement, property } from 'lit/decorators.js';
 import { UmbLitElement } from '@umbraco-cms/internal/lit-element';
 import type { UmbControllerHostElement } from '@umbraco-cms/backoffice/controller';
+import type { UmbContextToken } from '@umbraco-cms/backoffice/context-api';
 
+/**
+ * Provides a value to the context down the DOM tree.
+ *
+ * @remarks This element is a wrapper around the `provideContext` function.
+ * @slot - The context will be available to all descendants given in the default slot.
+ * @throws {Error} If the key property is not set.
+ * @throws {Error} If the value property is not set.
+ */
 @customElement('umb-context-provider')
 export class UmbContextProviderElement extends UmbLitElement {
 	/**
 	 * The value to provide to the context.
-	 * @required
+	 * @optional
 	 */
 	@property({ type: Object, attribute: false })
 	create?: (host: UmbControllerHostElement) => unknown;
@@ -24,7 +33,7 @@ export class UmbContextProviderElement extends UmbLitElement {
 	 * @required
 	 */
 	@property({ type: String })
-	key!: string;
+	key!: string | UmbContextToken;
 
 	connectedCallback() {
 		super.connectedCallback();

src/Umbraco.Web.UI.Client/src/installer/shared/utils.story-helpers.ts

@@ -1,6 +1,5 @@
 import { html } from 'lit';
 import { UmbInstallerContext } from '../installer.context';
-import '../../../storybook/utils/context-provider/context-provider.element';
 
 export const installerContextProvider = (story: any, installerContext = new UmbInstallerContext()) => html`
 	<umb-context-provider