feat: add canonical links to equivalent 2025 pages (#136)

## Overview

This should help with SEO prioritizing the older, more established 2024
domain over 2025.

Author: JoshuaKGoldberg

src/components/Head.astro

@@ -1,10 +1,11 @@
 ---
 export interface Props {
+	canonical?: string;
 	description: string;
 	title?: string;
 }
 
-const { description } = Astro.props;
+const { canonical, description } = Astro.props;
 
 const image = new URL("favicon.png", Astro.site).toString();
 
@@ -98,6 +99,7 @@ const metaPairs = [
 	<meta charset="utf-8" />
 	<link href="/favicon.png" rel="icon" type="image/svg+xml" />
 	<link href="/apple-touch-icon.png" rel="apple-touch-icon" sizes="180x180" />
+	{canonical && <link rel="canonical" href={canonical} />}
 	{metaPairs.map((meta) => <meta {...meta} />)}
 	<meta content={description} name="description" />
 	<meta content={keywords.join()} name="keywords" />

src/pages/about.astro

@@ -87,6 +87,7 @@ const brandingAssets = [
 ---
 
 <ContentLayout
+	canonical="https://2025.squiggleconf.com/about"
 	description="About SquiggleConf: a Boston conference focused on excellent web dev tooling."
 	title="About Us"
 >

src/pages/code-of-conduct.astro

@@ -5,6 +5,7 @@ import ContentLayout from "~/layouts/ContentLayout.astro";
 ---
 
 <ContentLayout
+	canonical="https://2025.squiggleconf.com/code-of-conduct"
 	description="Code of Conduct for SquiggleConf: a Boston conference focused on excellent web dev tooling."
 	title="Code of Conduct"
 >

src/pages/faqs.astro

@@ -6,6 +6,7 @@ import BodyText from "~/components/BodyText.astro";
 ---
 
 <ContentLayout
+	canonical="https://2025.squiggleconf.com/faqs"
 	description="FAQs for SquiggleConf: a Boston conference focused on excellent web dev tooling."
 	title="FAQs"
 >

src/pages/index.astro

@@ -11,6 +11,7 @@ import ContentLayout from "~/layouts/ContentLayout.astro";
 ---
 
 <ContentLayout
+	canonical="https://2025.squiggleconf.com"
 	description="A Boston conference focused on excellent web dev tooling."
 >
 	<PrimaryHero slot="hero" />