Use new template forms for issue templates

[flip1995]

GitHub has a new way to define issue templates. This gives an even more consistent formatting of our issues.

You can find (read-only) rendered versions here. If you want to try to fill out this kind of issue, you can do this in the cargo Repo.

changelog: Better issue templates

[rust-highfive]

r? @camsteffen

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[flip1995]

Of course there is still the question if we want to do this. I'll bring it up in the meeting on Tuesday.

[xFrednet]

Very fancy, I like this a lot! 👍

[camsteffen]

I'd like to see error output for false positive and lint name (optional) for new lint. But that's orthogonal to using the fancy new forms, so I think this is good!

[flip1995]

I'd like to see error output for false positive

I modified the default value of the text area. I think adding an additional section for just an error output would be overkill.

[camsteffen]

r=me after squash. Thanks!

[flip1995]

Rebased+Squashed. Let's get this merged.

@bors r=camsteffen

[bors]

📌 Commit 11002c7 has been approved by camsteffen

[bors]

⌛ Testing commit 11002c7 with merge abaffa7...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: camsteffen
Pushing abaffa7 to master...