Add markdown-link-check to index

Author: yorinasub17

README.md

@@ -13,7 +13,8 @@ supported hooks are:
 * **golint**: Automatically run `golint` on all Golang code (`*.go` files)
 * **yapf**: Automatically run [`yapf`](https://github.com/google/yapf) on all python code (`*.py` files).
 * **helmlint** Automatically run [`helm lint`](https://github.com/helm/helm/blob/master/docs/helm/helm_lint.md) on your
-  helm charts.
+* **markdown-link-check** Automatically run [markdown-link-check](https://github.com/tcort/markdown-link-check) on
+  markdown doc files.