feat(theme): allow hiding navbar on specific pages via frontmatter (#2565)

Author: keer-tea

src/client/theme-default/Layout.vue

@@ -39,7 +39,7 @@ provide('hero-image-slot-exists', heroImageSlotExists)
     <slot name="layout-top" />
     <VPSkipLink />
     <VPBackdrop class="backdrop" :show="isSidebarOpen" @click="closeSidebar" />
-    <VPNav>
+    <VPNav v-if="frontmatter.navbar !== false">
       <template #nav-bar-title-before><slot name="nav-bar-title-before" /></template>
       <template #nav-bar-title-after><slot name="nav-bar-title-after" /></template>
       <template #nav-bar-content-before><slot name="nav-bar-content-before" /></template>