Fix indentation in CI yaml

doc/ci/yaml/README.md

@@ -88,7 +88,7 @@ The example below simply moves all files from the root of the project to the
 `public/` directory. The `.public` workaround is so `cp` doesn't also copy
 `public/` to itself in an infinite loop:
 
-```
+```yaml
 pages:
   stage: deploy
   script:
@@ -131,7 +131,7 @@ if you set it per-job:
 
 ```yaml
 before_script:
-- global before script
+  - global before script
 
 job:
   before_script:
@@ -442,11 +442,11 @@ For example:
 
 ```yaml
 stages:
-- build
-- cleanup_build
-- test
-- deploy
-- cleanup
+  - build
+  - cleanup_build
+  - test
+  - deploy
+  - cleanup
 
 build_job:
   stage: build