Added test readme doc (#108)

test/README.md

+# Charts Testing
+
+### Lint Testing
+
+Lint testing is performed on every pull request and is run by the Drone CI. The
+configuration is stored in the [`test/ct.yaml`](/test/ct.yaml) file.
+
+The Lint Testing currently:
+
+* Performs [`ct lint`](https://github.com/guangbochen/chart-testing) on any changed charts to provide quick feedback
+
+
+#### Run Lint Testing Locally
+
+##### Using Docker Images:
+
+```
+docker run -d -it --name chart-test -v /path/to/your/charts/:/workdir/charts guangbo/chart-testing:v2.0.2-rancher1
+docker exec -it chart-test sh 
+cd workdir/charts/
+git remote add rancher-charts https://github.com/rancher/charts
+git fetch rancher-charts master
+ct lint --config test/ct.yaml
+```
+
+##### Using Binary Build:
+
+You can download the [binary build](https://github.com/guangbochen/chart-testing/releases/tag/v2.0.2-rancher1) and run it locally using:
+
+```
+ct lint --config /path/to/your/charts/test/ct.yaml
+```