Support 500 pages in the dev server (#131)

* Support 500 pages

* Document custom 400/500 pages

* Remove search from any pages not the 500 page

* fix(kitchen-sink): add snowpack.config.js

* fix(examples): add snowpack.config.js

* style: redesign built-in 500 page

Co-authored-by: Nate Moore <nate@skypack.dev>

1 files changed, 51 insertions, 0 deletions

diff --git a/docs/dev.md b/docs/dev.md
new file mode 100644
index 000000000..7b811d7d3
--- /dev/null
+++ b/docs/dev.md
@@ -0,0 +1,51 @@
+# Development Server
+
+The development server comes as part of the Astro CLI. Start the server with:
+
+```shell
+astro dev
+```
+
+In your project root. You can specify an alternative
+
+## Special routes
+
+The dev server will serve the following special routes:
+
+### /400
+
+This is a custom __400__ status code page. You can add this route by adding a page component to your `astro/pages` folder:
+
+```
+├── astro/
+│   ├── components/
+│   └── pages/
+│       └── 400.astro
+```
+
+For any URL you visit that doesn't have a corresponding page, the `400.astro` file will be used.
+
+### /500
+
+This is a custom __500__ status code page. You can add this route by adding a page component to your `astro/pages` folder:
+
+```astro
+├── astro/
+│   ├── components/
+│   └── pages/
+│       └── 500.astro
+```
+
+This page is used any time an error occurs in the dev server.
+
+The 500 page will receive an `error` query parameter which you can access with:
+
+```
+---
+const error = import.meta.request.url.searchParams.get('error');
+---
+
+<strong>{error}</strong>
+```
+
+A default error page is included with Astro so you will get pretty error messages even without adding a custom 500 page.
\ No newline at end of file