Bump fastimage from 2.2.4 to 2.3.1

Bumps [fastimage](https://github.com/sdsykes/fastimage) from 2.2.4 to 2.3.1.
- [Changelog](https://github.com/sdsykes/fastimage/blob/master/CHANGELOG)
- [Commits](sdsykes/fastimage@v2.2.4...v2.3.1)

---
updated-dependencies:
- dependency-name: fastimage
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile.lock

@@ -14,7 +14,7 @@ GEM
     faraday-excon (1.1.0)
     faraday-net_http (1.0.1)
     faraday-net_http_persistent (1.1.0)
-    fastimage (2.2.4)
+    fastimage (2.3.1)
     method_source (1.0.0)
     minitest (5.14.4)
     multipart-post (2.1.1)