Add circle-ci config to install yamllint in the CI env

Signed-off-by: Michal Wasilewski <mwasilewski@gmx.com>

.circleci/config.yml

@@ -28,6 +28,8 @@ jobs:
         keys:
         - v3-npm-deps-{{ checksum "web/ui/react-app/yarn.lock" }}
         - v3-npm-deps-
+    - run:
+        command: sudo apt-get install -y yamllint
     - run:
         command: make
         environment:
@@ -99,6 +101,8 @@ jobs:
     - run:
         command: jb install
         working_directory: ~/project/documentation/prometheus-mixin
+    - run:
+        command: sudo apt-get install -y yamllint
     - run:
         command: make
         working_directory: ~/project/documentation/prometheus-mixin