Fix issue template formatting (#6626)

* Fix issue template formatting

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Add additional mdformat plugins

* Fix bug_report.md

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

.github/ISSUE_TEMPLATE/bug_report.md

@@ -1,6 +1,10 @@
-______________________________________________________________________
+---
+name: Is this a bug in Notebook? Open an issue.
+about: If you're not sure, feel free to post your question on Jupyter's Discourse
+  channel.
 
-## name: Is this a bug in Notebook? Open an issue. about: If you're not sure, feel free to post your question on Jupyter's Discourse channel. labels: bug
+labels: bug
+---
 
 <!--
 BEFORE YOU OPEN AN ISSUE, PLEASE READ THIS.

.pre-commit-config.yaml

@@ -46,6 +46,8 @@ repos:
     rev: 0.7.16
     hooks:
       - id: mdformat
+        additional_dependencies:
+          [mdformat-gfm, mdformat-frontmatter, mdformat-footnote]
 
   - repo: https://github.com/john-hen/Flake8-pyproject
     rev: 1.2.1