Fix up chart linting, add docs and lint script (#146)

This updates the Helm linting system with the following changes:

- Import lintconf.yaml with small change to comment distance in order to
match existing values.yaml standards
- Update Chart.yaml and values.yaml in each chart to pass linting
standards
- Maintainers added to each chart from OWNERS + CODEOWNERS, the linter
requires GitHub usernames so argo-events maintainer names were converted
- README updated with documentation around chart standards and testing
- A local shell script added for running lint tests locally

CONTRIBUTING.md

@@ -51,6 +51,33 @@ argocd app create guestbook --dest-namespace default --dest-server https://kuber
 argocd app sync guestbook
 ```
 
+## New Application Versions
+
+When raising application versions ensure you make the following changes:
+
+- `values.yaml`: Bump all instances of the container image version
+- `Chart.yaml`: Ensure `appVersion` matches the above container image and bump `version`
+
+Please ensure chart version changes adhere to semantic versioning standards:
+
+- Patch: App version patch updates, backwards compatible optional chart features
+- Minor: New chart functionality (sidecars), major application updates or minor non-backwards compatible changes
+- Major: Large chart rewrites, major non-backwards compatible or destructive changes
+
+## Testing Charts
+
+As part of the Continous Intergration system we run Helm's [Chart Testing](https://github.com/helm/chart-testing) tool.
+
+The checks for this tool are stricter than the standard Helm requirements, where fields normally considered optional like `maintainer` are required in the standard spec and must be valid GitHub usernames.
+
+Linting configuration can be found in [lintconf.yaml](.circleci/lintconf.yaml)
+
+The linting can be invoked manually with the following command:
+
+```
+./scripts/lint.sh
+```
+
 ## Publishing Changes
 
 Changes are automatically publish whenever a commit is merged to master. The CI job (see `.circleci/config.yaml`) runs this: