Added Toggle Indexes (#4544)

* Add monochrome theme with grayscale filter

* Add indexes toggle and disable starred

* Keep filters mutually exclusive

docs/.vitepress/theme/components/ToggleIndexes.vue

@@ -0,0 +1,23 @@
+<script setup lang="ts">
+import Switch from './Switch.vue'
+
+const toggleIndexes = () => {
+  const root = document.documentElement
+  const enabling = !root.classList.contains('indexes-only')
+  root.classList.toggle('indexes-only')
+
+  if (enabling && root.classList.contains('starred-only')) {
+    root.classList.remove('starred-only')
+  }
+}
+</script>
+
+<template>
+  <Switch @click="toggleIndexes()" />
+</template>
+
+<style>
+.indexes-only li:not(.index) {
+  display: none;
+}
+</style>