Use the form version of the issue templates

[vicb]

We added templates in https://github.com/opennextjs/opennextjs-cloudflare/pull/124

We should switch to the form version of the templates

refs:

• https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/syntax-for-issue-forms
• https://github.com/vercel/next.js/blob/224447cd/.github/ISSUE_TEMPLATE/1.bug_report.yml?plain=1