Merge branch 'otp21' into 'master'

gitlab-ci: test with 21

See merge request triq/triq!26
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 7a183d1..7da1f26 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -14,7 +14,7 @@
 
 variables:
   GIT_DEPTH: "3"
-  DEFAULT_IMAGE: erlang:20-alpine
+  DEFAULT_IMAGE: erlang:21-alpine
 
 pages:
   stage: deploy
@@ -90,6 +90,12 @@
   <<: *test_job_definition
   before_script:
     - apk add --update make
+  image: erlang:20-alpine
+
+test:21:
+  <<: *test_job_definition
+  before_script:
+    - apk add --update make
   image: $DEFAULT_IMAGE
 
 test:dialyze: