feat: add %sveltekit.version% placeholder for template interpolation (#12132)

* feat:  Add %sveltekit.version% placeholder for template interpolation

* docs

* changeset

* oops

* escape

---------

Co-authored-by: Rich Harris <[email protected]>

Author: potch

.changeset/twelve-cows-hear.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': minor
+---
+
+feat: add `%sveltekit.version%` to `app.html`

documentation/docs/10-getting-started/30-project-structure.md

@@ -52,6 +52,7 @@ The `src` directory contains the meat of your project. Everything except `src/ro
 - `error.html` is the page that is rendered when everything else fails. It can contain the following placeholders:
   - `%sveltekit.status%` — the HTTP status
   - `%sveltekit.error.message%` — the error message
+  - `%sveltekit.version%` — the deployment version, which can be specified with the [`version`](configuration#version) configuration
 - `hooks.client.js` contains your client [hooks](hooks)
 - `hooks.server.js` contains your server [hooks](hooks)
 - `service-worker.js` contains your [service worker](service-workers)

packages/kit/src/core/sync/write_server.js

@@ -7,6 +7,7 @@ import { load_error_page, load_template } from '../config/index.js';
 import { runtime_directory } from '../utils.js';
 import { isSvelte5Plus, write_if_changed } from './utils.js';
 import colors from 'kleur';
+import { escape_html } from '../../utils/escape.js';
 
 /**
  * @param {{
@@ -54,6 +55,7 @@ export const options = {
 			.replace('%sveltekit.body%', '" + body + "')
 			.replace(/%sveltekit\.assets%/g, '" + assets + "')
 			.replace(/%sveltekit\.nonce%/g, '" + nonce + "')
+			.replace(/%sveltekit\.version%/g, escape_html(config.kit.version.name))
 			.replace(
 				/%sveltekit\.env\.([^%]+)%/g,
 				(_match, capture) => `" + (env[${s(capture)}] ?? "") + "`