chore: add issue template config to redirect claim namespace issues

Author: netomi

.github/ISSUE_TEMPLATE/config.yml

@@ -1,8 +1,5 @@
 blank_issues_enabled: true
 contact_links:
   - name: Claiming namespace ownership
-    url: https://github.com/EclipseFdn/open-vsx.org/issues/new/choose
-    about: Claiming ownership of a namespace on open-vsx.org.
-  - name: Remove extension request
-    url: https://github.com/EclipseFdn/open-vsx.org/issues/new/choose
-    about: Requesting to remove an extension hosted on open-vsx.org.
+    url: https://github.com/EclipseFdn/open-vsx.org/issues/new?template=claim-namespace-ownership.md
+    about: Claiming ownership of a namespace on https://open-vsx.org.