added drone config and helm lint for charts validation

.drone.yml

+pipeline:
+  lint-charts:
+    image: guangbo/chart-testing:v1.0.3
+    commands:
+      - git remote add rancher-charts https://github.com/rancher/charts
+      - git fetch rancher-charts master
+      - chart_test.sh --config test/.testenv --no-install

.gitignore

+.DS_Store

test/.dockerignore

+*
+! .testenv

test/.testenv

+# The name of the Git remote to check against for changed charts
+REMOTE=rancher-charts
+
+# The name of the Git target branch
+TARGET_BRANCH=master
+
+# Chart directories separated by a space
+CHART_DIRS=(
+    charts
+    proposed
+)
+
+# Charts that should be skipped
+EXCLUDED_CHARTS=(
+)
+
+# Additional chart repos to add (<name>=<url>), separated by a space
+CHART_REPOS=(
+)
+
+# Timeout for chart installation in seconds
+TIMEOUT=600
+
+# Maintainer names in Chart.yaml are validated to be existing Github accounts, default to true
+VALIDATE_MAINTAINERS=true