Adding a Bug issue template (#930)

* Create bug.yaml

* Update bug.yaml - Case consistency

* Spelling mistakes

.github/ISSUE_TEMPLATE/bug.yaml

@@ -0,0 +1,18 @@
+name: CVA6 bug
+description: Create a CVA6 bug
+title: "[BUG] <title>"
+labels: ["Type:Bug"]
+body:
+- type: checkboxes
+  attributes:
+    label: Is there an existing CVA6 bug for this?
+    description: Please search to see if an issue already exist for the bug you need to create
+    options:
+    - label: I have searched the existing bug issues
+      required: true
+- type: textarea
+  attributes:
+    label: Bug Description
+    description: A concise description of the bug
+  validations:
+    required: true