Improve the bug reporting template (#4554)

Author: sigurdm

.github/ISSUE_TEMPLATE/2-BUG.md

@@ -6,11 +6,15 @@ about: The pub client is printing a stack trace or failing unexpectedly.
 
 # Environment
 
-- Dart version (run `dart --version`):
+<!--
+Describe anything relevant to the issue you are seeing. Consider including:
+- Dart/Flutter version (run `dart --version` or `flutter --version`):
 - OS kind and version (e.g. "Windows 10, version 1809" or "macOS 12.4"):
+- In case of network issues
+  * consider running https://github.com/dart-lang/pub-dev/blob/master/app/bin/tools/check_domain_access.dart
+  and adding the output.
 - Are you using the Chinese community mirror or a corporate firewall?
 
-<!--
   Resources:
   https://flutter.dev/community/china
   https://www.dart.dev/tools/pub/troubleshoot#pub-get-fails-from-behind-a-corporate-firewall
@@ -43,8 +47,10 @@ about: The pub client is printing a stack trace or failing unexpectedly.
   What actually happened?
 -->
 
-## --trace output
+## `--verbose` output
 
-```
-<copy/paste the full output>
-```
+<!--
+Consider attaching the full output run with `--verbose` if relevant.
+
+https://docs.github.com/en/get-started/writing-on-github/working-with-advanced-formatting/attaching-files
+-->