prerelease pr badge

Author: mbostock

docs/.vitepress/theme/VersionBadge.vue

@@ -1,12 +1,12 @@
 <script setup>
 
-const {version} = defineProps(["version"]);
+const {version, pr} = defineProps(["version", "pr"]);
 
 </script>
 <template>
-  <Badge type="tip">
-    <a :href="`https://github.com/observablehq/plot/releases/tag/v${version}`" :title="`added in v${version}`" target="_blank" rel="external" style="color: inherit;">
-      ^{{ version }}
+  <Badge v-if="version || pr" :type="version ? `tip` : `warning`">
+    <a :href="version ? `https://github.com/observablehq/plot/releases/tag/v${version}` : `https://github.com/observablehq/plot/pull/${pr}`" :title="version ? `added in v${version}` : `added in #${pr}`" target="_blank" rel="external" style="color: inherit;">
+      {{ version ? `^${version}` : "prerelease" }}
     </a>
   </Badge>
 </template>

docs/marks/bollinger.md

@@ -10,7 +10,7 @@ const k = ref(2);
 
 </script>
 
-# Bollinger mark <Badge type="warning" text="prerelease" />
+# Bollinger mark <VersionBadge pr="1772" />
 
 The **bollinger mark** is a [composite mark](../features/marks.md#marks) consisting of a [line](./line.md) representing a moving average and an [area](./area.md) representing volatility as a band; the band thickness is proportional to the deviation of nearby values. The bollinger mark is often used to analyze the price of financial instruments such as stocks.