docs: add delete-dependency-<id> to README (#556)

Signed-off-by: Dmitry Mordvinov <dmitry.mordvinov@flant.com>

Author: dmmordvi

README.md

@@ -44,6 +44,7 @@ Nelm is production-ready: as the werf deployment engine, it was battle-tested ac
 - [Reference](#reference)
   - [`werf.io/weight` annotation](#werfioweight-annotation)
   - [`werf.io/deploy-dependency-<id>` annotation](#werfiodeploy-dependency-id-annotation)
+  - [`werf.io/delete-dependency-<id>` annotation](#werfiodelete-dependency-id-annotation)
   - [`<id>.external-dependency.werf.io/resource` annotation](#idexternal-dependencywerfioresource-annotation)
   - [`<id>.external-dependency.werf.io/name` annotation](#idexternal-dependencywerfioname-annotation)
   - [`werf.io/ownership` annotation](#werfioownership-annotation)
@@ -351,7 +352,7 @@ Default:
 
 ### `werf.io/deploy-dependency-<id>` annotation 
 
-The resource will deploy only after all of its dependencies are satisfied. It waits until the specified resource is just `present` or is also `ready`. It serves as a more powerful alternative to hooks and `werf.io/weight`. You can only point to resources in the release. This annotation has higher priority than `werf.io/weight` and `helm.sh/hook-weight`.
+The resource will deploy only after all of its dependencies are satisfied. It waits until the specified resource is just `present` or is also `ready`. It serves as a more powerful alternative to hooks and `werf.io/weight`. You can only point to resources in the release. This annotation has higher priority than `werf.io/weight` and `helm.sh/hook-weight`. This annotation has no effect if the resource on which we depend upon is outside the stage (pre, main, post, ...) of the resource with the annotation.
 
 Example:
 ```yaml
@@ -363,6 +364,20 @@ Format:
 werf.io/deploy-dependency-<anything>: state=ready|present[,name=<name>][,namespace=<namespace>][,kind=<kind>][,group=<group>][,version=<version>]
 ```
 
+### `werf.io/delete-dependency-<id>` annotation
+
+The resource will be deleted only after all of its dependencies are satisfied. It waits until the specified resource is `absent`. You can only point to resources in the release. This annotation has no effect if the resource on which we depend upon is outside the stage (pre, main, post, ...) of the resource with the annotation.
+
+Example:
+```yaml
+werf.io/delete-dependency-db: state=absent,kind=StatefulSet,name=postgres
+werf.io/delete-dependency-app: state=absent,kind=Deployment,group=apps,version=v1,name=app,namespace=app
+```
+Format:
+```
+werf.io/delete-dependency-<anything>: state=absent[,name=<name>][,namespace=<namespace>][,kind=<kind>][,group=<group>][,version=<version>]
+```
+
 ### `<id>.external-dependency.werf.io/resource` annotation 
 
 The resource will deploy only after all of its external dependencies are satisfied. It waits until the specified resource is `present` and `ready`. You can only point to resources outside the release.