chore (website): add deployed examples to demos on website (#2186)

This adds all of the deployed examples as demos on the website.

website/demos/nextjs.md

@@ -2,7 +2,9 @@
 title: Next.js
 description: >-
   Example of an Electric app using Next.js.
+deployed_url: https://nextjs.examples.electric-sql.com/
 source_url: https://github.com/electric-sql/electric/tree/main/examples/nextjs
+image: /img/demos/items-screenshot.png
 example: true
 ---
 

website/demos/proxy-auth.md

@@ -2,7 +2,9 @@
 title: Proxy auth
 description: >-
   Example showing how to authorize access to Electric using a proxy.
+deployed_url: https://proxy-auth.examples.electric-sql.com/
 source_url: https://github.com/electric-sql/electric/tree/main/examples/proxy-auth
+image: /img/demos/proxy-auth-screenshot.png
 example: true
 ---
 

website/demos/react.md

@@ -2,7 +2,9 @@
 title: React
 description: >-
   Basic example of an Electric app using React.
+deployed_url: https://basic.examples.electric-sql.com
 source_url: https://github.com/electric-sql/electric/tree/main/examples/react
+image: /img/demos/items-screenshot.png
 example: true
 ---
 

website/demos/remix.md

@@ -2,7 +2,9 @@
 title: Remix
 description: >-
   Example of an Electric app using Remix.
+deployed_url: https://remix.examples.electric-sql.com/
 source_url: https://github.com/electric-sql/electric/tree/main/examples/nextjs
+image: /img/demos/items-screenshot.png
 example: true
 ---
 

website/demos/tanstack.md

@@ -2,7 +2,9 @@
 title: Tanstack
 description: >-
   Example of an Electric app using Tanstack Query for optimistic state.
+deployed_url: https://tanstack.examples.electric-sql.com/
 source_url: https://github.com/electric-sql/electric/tree/main/examples/tanstack
+image: /img/demos/items-screenshot.png
 example: true
 ---