Fix the document issue template to make it valid (#3840)

Author: daxian-dbw

.github/ISSUE_TEMPLATE/Documentation_Issue.yaml

@@ -8,3 +8,9 @@ body:
       Thanks for taking the time to fill out this documentation Issue! |
       Documents for PSReadLine are hosted in the [PowerShell-Docs](https://github.com/MicrosoftDocs/PowerShell-Docs) repo, |
       so, please submit the issue directly in that repo for a quicker response and fix.
+- type: checkboxes
+  attributes:
+    label: Prerequisites
+    options:
+    - label: Write a descriptive title.
+      required: true