Bump thruster from 0.1.16 to 0.1.21 (#89)

Bumps [thruster](https://github.com/basecamp/thruster) from 0.1.16 to 0.1.21.
- [Changelog](https://github.com/basecamp/thruster/blob/main/CHANGELOG.md)
- [Commits](basecamp/thruster@v0.1.16...v0.1.21)

---
updated-dependencies:
- dependency-name: thruster
  dependency-version: 0.1.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -523,10 +523,10 @@ GEM
       railties (>= 6.0.0)
     stringio (3.1.7)
     thor (1.3.2)
-    thruster (0.1.16)
-    thruster (0.1.16-aarch64-linux)
-    thruster (0.1.16-arm64-darwin)
-    thruster (0.1.16-x86_64-linux)
+    thruster (0.1.21)
+    thruster (0.1.21-aarch64-linux)
+    thruster (0.1.21-arm64-darwin)
+    thruster (0.1.21-x86_64-linux)
     tilt (2.6.0)
     timeout (0.4.3)
     turbo-rails (2.0.13)