Suggest using code-fences in bug template (#4556)

Author: sigurdm

.github/ISSUE_TEMPLATE/2-BUG.md

@@ -15,6 +15,9 @@ Describe anything relevant to the issue you are seeing. Consider including:
   and adding the output.
 - Are you using the Chinese community mirror or a corporate firewall?
 
+Please use [code fences](https://help.github.com/en/github/writing-on-github/creating-and-highlighting-code-blocks) 
+when posting logs or code, for large log files please attach them or use a [gist](https://gist.github.com/)
+
   Resources:
   https://flutter.dev/community/china
   https://www.dart.dev/tools/pub/troubleshoot#pub-get-fails-from-behind-a-corporate-firewall
@@ -50,7 +53,9 @@ Describe anything relevant to the issue you are seeing. Consider including:
 ## `--verbose` output
 
 <!--
-Consider attaching the full output run with `--verbose` if relevant.
+Consider attaching parts of or the full output run with `--verbose` if relevant.
+
+Please use [code fences](https://help.github.com/en/github/writing-on-github/creating-and-highlighting-code-blocks), for large log files please attach them or use a [gist](https://gist.github.com/)
 
 https://docs.github.com/en/get-started/writing-on-github/working-with-advanced-formatting/attaching-files
 -->