breaking(ui-shell): remove GlobalHeader, SideNav folders (#1223)

* breaking(ui-shell): remove GlobalHeader/SideNav folders

* Run "yarn build:docs"

src/UIShell/HeaderNavMenu.svelte

@@ -0,0 +1,105 @@
+<script>
+  /** Set to `true` to toggle the expanded state */
+  export let expanded = false;
+
+  /** Specify the `href` attribute */
+  export let href = "/";
+
+  /**
+   * Specify the text
+   * @type {string}
+   */
+  export let text = undefined;
+
+  /** Obtain a reference to the HTML anchor element */
+  export let ref = null;
+
+  import { setContext } from "svelte";
+  import { writable } from "svelte/store";
+  import ChevronDown16 from "../icons/ChevronDown16.svelte";
+
+  const selectedItems = writable({});
+
+  let menuRef = null;
+
+  setContext("HeaderNavMenu", {
+    selectedItems,
+    updateSelectedItems(item) {
+      selectedItems.update((_items) => ({
+        ..._items,
+        [item.id]: item.isSelected,
+      }));
+    },
+    closeMenu() {
+      expanded = false;
+    },
+  });
+
+  $: isCurrentSubmenu =
+    Object.values($selectedItems).filter(Boolean).length > 0;
+</script>
+
+<svelte:window
+  on:click="{({ target }) => {
+    if (!ref.contains(target)) {
+      expanded = false;
+    }
+  }}"
+/>
+
+<li
+  role="none"
+  class:bx--header__submenu="{true}"
+  class:bx--header__submenu--current="{isCurrentSubmenu}"
+  on:click="{(e) => {
+    if (!menuRef.contains(e.target)) {
+      e.preventDefault();
+    }
+    expanded = !expanded;
+  }}"
+  on:keydown="{(e) => {
+    if (e.key === 'Enter') {
+      e.stopPropagation();
+      expanded = !expanded;
+    }
+  }}"
+>
+  <a
+    bind:this="{ref}"
+    role="menuitem"
+    tabindex="0"
+    aria-haspopup="menu"
+    aria-expanded="{expanded}"
+    aria-label="{text}"
+    href="{href}"
+    class:bx--header__menu-item="{true}"
+    class:bx--header__menu-title="{true}"
+    {...$$restProps}
+    style="{$$restProps.style}; z-index: 1"
+    on:keydown
+    on:keydown="{(e) => {
+      if (e.key === ' ') e.preventDefault();
+      if (e.key === 'Enter' || e.key === ' ') {
+        expanded = !expanded;
+      }
+    }}"
+    on:click|preventDefault
+    on:mouseover
+    on:mouseenter
+    on:mouseleave
+    on:keyup
+    on:focus
+    on:blur
+  >
+    {text}
+    <ChevronDown16 class="bx--header__menu-arrow" />
+  </a>
+  <ul
+    bind:this="{menuRef}"
+    role="menu"
+    aria-label="{text}"
+    class:bx--header__menu="{true}"
+  >
+    <slot />
+  </ul>
+</li>