docs: add Navbar component

Author: PeachScript

docs/.vuepress/theme/Navbar.vue

@@ -0,0 +1,51 @@
+<template>
+  <nav>
+    <router-link
+      v-for="(nav, $index) in navs"
+      :key="$index"
+      v-if="!/^http/.test(nav.link)"
+      v-text="nav.text"
+      :to="nav.link">
+    </router-link>
+    <a target="_blank" :href="nav.link" v-else>{{ nav.text }}<outbound-link/></a>
+
+    <a
+      v-if="$site.themeConfig.repo"
+      target="_blank"
+      :href="$site.themeConfig.repo">GitHub<outbound-link/></a>
+  </nav>
+</template>
+
+<script>
+export default {
+  computed: {
+    navs() {
+      return this.$themeLocaleConfig.nav || this.$site.themeConfig.nav || [];
+    },
+  },
+};
+</script>
+
+<style lang="less" scoped>
+@import './less/variables.less';
+
+nav {
+  float: right;
+  padding: 20px 0;
+
+  a {
+    color: @c-basic;
+    margin-left: 35px;
+    transition: font-weight 0.2s;
+
+    &:not(:hover) {
+      text-decoration: none;
+    }
+
+    &.router-link-active {
+      font-weight: bold;
+      color: lighten(@c-basic, 10%);
+    }
+  }
+}
+</style>