Bump css_parser from 1.22.0 to 3.0.0 in /demo

Bumps [css_parser](https://github.com/premailer/css_parser) from 1.22.0 to 3.0.0.
- [Changelog](https://github.com/premailer/css_parser/blob/master/CHANGELOG.md)
- [Commits](premailer/css_parser@v1.22.0...v3.0.0)

---
updated-dependencies:
- dependency-name: css_parser
  dependency-version: 3.0.0
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

demo/Gemfile.lock

@@ -63,8 +63,9 @@ GEM
     concurrent-ruby (1.3.7)
     connection_pool (3.0.2)
     crass (1.0.7)
-    css_parser (1.22.0)
+    css_parser (3.0.0)
       addressable
+      ssrf_filter (~> 1.5)
     cssbundling-rails (1.4.3)
       railties (>= 6.0.0)
     date (3.5.1)
@@ -341,6 +342,7 @@ GEM
       actionpack (>= 6.1)
       activesupport (>= 6.1)
       sprockets (>= 3.0.0)
+    ssrf_filter (1.5.0)
     statsd-instrument (3.9.9)
     stimulus-rails (1.3.4)
       railties (>= 6.0.0)