add chart linting step to drone pipeline (#1207)

.drone.yml

@@ -3,6 +3,18 @@ kind: pipeline
 name: default
 
 steps:
+
+- name: chart-lint
+  image: quay.io/helmpack/chart-testing:v2.3.3
+  commands:
+  - ct lint --config test/ct.yaml
+  when:
+    branch:
+      - master
+    event:
+      - push
+      - pull_request
+
 - name: build
   image: golang:1.12
   commands:

test/ct.yaml

@@ -0,0 +1,4 @@
+target-branch: master
+chart-dirs:
+  - charts
+helm-extra-args: --timeout 800