feat: add StackBlitz starter link and convert /issue page to mdx

- Replace issue.tsx redirect with issue.mdx page that lets users choose
  between StackBlitz and CodeSandbox starter templates
- Update references in issues.mdx and contribute.mdx

Author: langz

packages/dnb-design-system-portal/src/docs/contribute.mdx

@@ -119,7 +119,7 @@ Colors, fonts and logo guidelines are set in the DNB Brandbook and the digital v
 
 [Jira Issue Tracking](https://dnb-asa.atlassian.net/jira/software/c/projects/EDS/summary) or [GitHub Issue Tracking](https://github.com/dnbexperience/eufemia/issues): Where you can report or find new issues
 
-[Codesandbox Template](https://eufemia.dnb.no/issue/): For quickly reproducing issues when reporting bugs.
+[Starter Templates](https://eufemia.dnb.no/issue/): For quickly reproducing issues when reporting bugs (StackBlitz or CodeSandbox).
 
 ### People of Eufemia
 

packages/dnb-design-system-portal/src/docs/contribute/style-guides/issues.mdx

@@ -13,7 +13,7 @@ bug report to the GitHub repository. Thanks for helping out.
 
 When reporting issues or suggesting new features, we would appreciate if you use [GitHub Issues](https://github.com/dnbexperience/eufemia/issues) or our [Jira Kanban board](https://dnb-asa.atlassian.net/jira/software/c/projects/EDS/summary). Another option is to send a Slack message in [#eufemia-web](https://dnb-it.slack.com/archives/CMXABCHEY).
 
-For reproduction of issues you can use our [codesandbox starter template](/issue/). Including this in your report helps us out a lot.
+For reproduction of issues you can use our [starter templates](/issue/) (StackBlitz or CodeSandbox). Including this in your report helps us out a lot.
 
 ## GitHub issues
 

packages/dnb-design-system-portal/src/docs/issue.mdx

@@ -0,0 +1,31 @@
+---
+title: 'Reproduce an issue'
+---
+
+import { Card, Flex, Anchor, P, Lead } from '@dnb/eufemia/src'
+
+# Reproduce an issue
+
+When reporting a bug, a minimal reproduction helps us identify and fix the problem faster. Choose one of the starter templates below to get started:
+
+<Flex.Horizontal top="large" gap="large">
+  <Card stack>
+    ### StackBlitz
+
+    <P>Open our StackBlitz starter template to create a reproduction right in the browser.</P>
+
+    <Anchor href="https://stackblitz.com/edit/u6dlg7ok?file=src%2FApp.tsx" target="_blank">
+      Open StackBlitz Starter
+    </Anchor>
+  </Card>
+
+  <Card stack>
+    ### CodeSandbox
+
+    <P>Open our CodeSandbox starter template to create a reproduction right in the browser.</P>
+
+    <Anchor href="https://codesandbox.io/s/eufemia-starter-0gcwo" target="_blank">
+      Open CodeSandbox Starter
+    </Anchor>
+  </Card>
+</Flex.Horizontal>