feat!: Improve Pull Request Template & Contributing Guidelines (#750)

* feat: improve documentation and require changelog

Signed-off-by: Oliver Bähler <oliverbaehler@hotmail.com>

* Bump Versions

Signed-off-by: Oliver Bähler <oliverbaehler@hotmail.com>

* Bump argo-rollouts

Signed-off-by: Marco Kilchhofer <mkilchhofer@users.noreply.github.com>

* Apply suggestions from code review

Signed-off-by: Marco Kilchhofer <mkilchhofer@users.noreply.github.com>

* Reword Artifacthub -> Artifact Hub

Signed-off-by: Marco Kilchhofer <mkilchhofer@users.noreply.github.com>

Co-authored-by: Marco Kilchhofer <mkilchhofer@users.noreply.github.com>

charts/argocd-notifications/Chart.yaml

@@ -3,7 +3,7 @@ appVersion: 1.1.1
 description: A Helm chart for ArgoCD notifications, an add-on to ArgoCD.
 name: argocd-notifications
 type: application
-version: 1.4.0
+version: 1.4.1
 home: https://github.com/argoproj/argo-helm
 icon: https://raw.githubusercontent.com/argoproj/argo/master/docs/assets/argo.png
 keywords:
@@ -13,3 +13,6 @@ keywords:
 maintainers:
   - name: alexmt
   - name: andyfeller
+annotations:
+  artifacthub.io/changes: |
+    - "[Added]: Initialize Changelog"