[MRG] MAINT: Use new GitHub issue forms (yml)

[sappelhoff]

PR Description

closes #1043

to get a preview of how it looks and feels, try opening an issue (bug or feature) here: https://github.com/bids-standard/bids-specification/issues/new/choose

Merge checklist

Maintainer, please confirm the following before merging.
If applicable:

• All comments are resolved
• This is not your own PR
• All CIs are happy
• PR title starts with [MRG]
• whats_new.rst is updated
• New contributors have been added to CITATION.cff
• PR description includes phrase "closes <#issue-number>"

[codecov]

Codecov Report

Merging #1056 (2ed9b9f) into main (3f77995) will not change coverage.
The diff coverage is n/a.

❗ Current head 2ed9b9f differs from pull request most recent head 876d61a. Consider uploading reports for the commit 876d61a to get more accurate results

@@           Coverage Diff           @@
##             main    #1056   +/-   ##
=======================================
  Coverage   95.21%   95.21%           
=======================================
  Files          25       25           
  Lines        3822     3822           
=======================================
  Hits         3639     3639           
  Misses        183      183           

Impacted Files	Coverage Δ
mne_bids/path.py	97.67% <0.00%> (ø)

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[hoechenberger]

Looks good, but can we preprend the items with some nice emojis?

• bug: 🐛 or 🐞
• feature request: 🛠
• forum: 💬
• BIDS spec: 📖

Also I'd add tags instead of preprending the titles. Like, add a bug label instead of disfiguring the title of an issue with [BUG].

Edit: I see we already add labels. So then I'd simply drop the prefixes.

[hoechenberger]

Thanks @sappelhoff!