docs: Examples for semver and digest update strategy (argoproj-labs#507)

Proposal examples to use semver and digest update strategy

Author: dmouse

docs/examples/index.md

@@ -1,7 +1,48 @@
 # Examples
 
-This chapter contains community contributed examples on how to configure Argo
-CD Image Updater for a certain registry or environment.
+## Digest
+Using `digest` sha configuration for `image-list`
 
-Feel free to submit your own examples or guides to the documentation, as we do
-not have access to all the registries and cloud platforms out there.
+```
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: dev
+  annotations:
+    argocd-image-updater.argoproj.io/write-back-method: argocd
+    argocd-image-updater.argoproj.io/image-list: api=registry.com/vendor/api:latest,front=registry.com/vendor/front:latest
+    argocd-image-updater.argoproj.io/update-strategy: digest
+---
+apiVersion: apps/v1
+kind: Deployment
+spec:
+  template:
+    spec:
+      containers:
+        - name: app
+          image: registry.com/vendor/api@sha256:38089... # Initial sha
+```
+
+## semver
+Using `semver` defining the `update-strategy` per `image-list`
+
+```
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: prod
+  annotations:
+    argocd-image-updater.argoproj.io/write-back-method: argocd
+    argocd-image-updater.argoproj.io/image-list: api=registry.com/vendor/api:1.x,front=registry.com/vendor/front:1.x
+    #argocd-image-updater.argoproj.io/update-strategy: semver # to apply for all the images
+    argocd-image-updater.argoproj.io/api.update-strategy: semver
+    argocd-image-updater.argoproj.io/front.update-strategy: semver
+---
+apiVersion: apps/v1
+kind: Deployment
+spec:
+  template:
+    spec:
+      containers:
+          image: registry.com/vendor/api:1.0
+```