fix(util): estimate reading time from plain text

src/utils/readingTime.ts

@@ -1,7 +1,13 @@
 export function estimateReadingTime(content: string = ''): string {
-  const noWhitespace = content.replace(/\s/g, '').length
-  const minutes = Math.ceil(noWhitespace / 400)
-  return `${minutes} 分钟`
+  const plain = content
+    .replace(/<[^>]*>/g, ' ')
+    .replace(/&[a-zA-Z#0-9]+;/g, ' ')
+    .replace(/\s+/g, ' ')
+    .trim()
+  const cjk = (plain.match(/[\u4e00-\u9fff\u3040-\u30ff\uac00-\ud7af]/g) ?? []).length
+  const words = plain.length === 0 ? 0 : plain.trim().split(/\s+/).length
+  const minutes = Math.max(1, Math.ceil((cjk + words) / 400))
+  return `约 ${minutes} 分钟`
 }
 
 export function formatDay(iso: string): string {