Issue submission form - preview should open links in a new tab

[shawnheide]

Steps to reproduce

Fill out the form on the issue helper (https://new-issue.vuejs.org/?repo=vuejs/vue). Click on the Preview button. Click on the link inside the preview window.

What is expected?

The link opens in a new tab.

What is actually happening?

The link opens in the current tab without submitting the issue. Going "back" in the browser results in an empty form.

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Sadly, I discovered this the hard way after trying to submit my first issue.

[shawnheide]

I looked into this and it looks like a limitation of the marked package. A workaround that was listed in a relevant issue on the marked repo suggested to simply extend the linkRenderer function. I'm creating a pull request with the suggested change.