Basic error checking

src/site/pug/friendlyerror.pug

@@ -0,0 +1,18 @@
+//- Needs title, message, statusCode
+
+include includes/timeline_page.pug
+include includes/next_page_button.pug
+
+- const numberFormat = new Intl.NumberFormat().format
+
+doctype html
+html
+	head
+		meta(charset="utf-8")
+		meta(name="viewport" content="width=device-width, initial-scale=1")
+		title= `${title} | Bibliogram`
+		link(rel="stylesheet" type="text/css" href="/static/css/main.css")
+	body.error-page
+		h1.code= statusCode
+		p.message= message
+		a(href="javascript:history.back()").back ← Go back?