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/argo-workflows/Chart.yaml

@@ -2,7 +2,7 @@ apiVersion: v2
 name: argo-workflows
 description: A Helm chart for Argo Workflows
 type: application
-version: 0.2.6
+version: 0.2.7
 appVersion: "v3.0.7"
 icon: https://raw.githubusercontent.com/argoproj/argo-workflows/master/docs/assets/argo.png
 home: https://github.com/argoproj/argo-helm
@@ -13,3 +13,6 @@ maintainers:
   - name: alexmt
   - name: jessesuen
   - name: benjaminws
+annotations:
+  artifacthub.io/changes: |
+    - "[Added]: Initialize Changelog"