github: Add fields to help users in the bug report

Not everyone filling out the bug report is an expert.
These fields, with additional explanations, can hopefully
help users provide more accurate information.

Add fields to guide users in completing the bug report.

Signed-off-by: Wesley Gimenes <wehagy@proton.me>
(cherry picked from commit 38b89da400)

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -20,6 +20,9 @@ body:
     id: maintainer
     attributes:
       label: Maintainer
+      description: |
+        Check the latest package commits and/or search the repo with the example below.\
+        ```<package-name>/makefile maintainer```
       placeholder: (@username)
     validations:
       required: true
@@ -28,6 +31,9 @@ body:
     id: openwrt-version
     attributes:
       label: OpenWrt Version
+      description: |
+        If you are unsure, use the command below.\
+        ```ubus call system board | jsonfilter -e '@.release.version'```
       placeholder: e.g. 23.05.2 or SNAPSHOT
     validations:
       required: true
@@ -36,6 +42,9 @@ body:
     id: target-subtarget
     attributes:
       label: OpenWrt Target/Subtarget
+      description: |
+        If you are unsure, use the command below.\
+        ```ubus call system board | jsonfilter -e '@.release.target'```
       placeholder: e.g. ramips/mt76x8, ath79/generic
     validations:
       required: true