Add contribution guide and issue templates

.github/ISSUE_TEMPLATE/enhancement.yml

@@ -0,0 +1,33 @@
+name: Enhancement
+description: Make a specific, well-motivated proposal for a feature.
+title: "[ENH]: ..."
+labels: [enhancement]
+
+
+body:
+- type: markdown
+  attributes:
+    value: >
+      Please post your idea first as a [Discussion](https://github.com/Akkudoktor-EOS/EOS/discussions)
+      to validate it and bring attention to it. After validation,
+      you can open this issue for a more technical developer discussion.
+      Check the [Contributor Guide](https://github.com/Akkudoktor-EOS/EOS/blob/main/CONTRIBUTING.md)
+      if you need more information.
+
+- type: textarea
+  attributes:
+    label: "Link to discussion and related issues"
+    description: >
+      <link here>
+    render: python
+  validations:
+    required: false
+
+- type: textarea
+  attributes:
+    label: "Proposed implementation"
+    description: >
+      How it could be implemented with a high level API.
+    render: python
+  validations:
+    required: false