Update pull_request_template.md

Include a reminder about adding a query to autofix,

.github/pull_request_template.md

@@ -11,3 +11,4 @@
 
 - [ ] Autofixes generated based on these changes are valid, only needed if this PR makes significant changes to `.ql`, `.qll`, or `.qhelp` files. See [the documentation](https://github.com/github/codeql-team/blob/main/docs/best-practices/validating-autofix-for-query-changes.md) (internal access required).
 - [ ] Changes are validated [at scale](https://github.com/github/codeql-dca/) (internal access required).
+- [ ] Adding a new query? Consider also [adding the query to autofix](https://github.com/github/codeml-autofix/blob/main/docs/updating-query-support.md#adding-a-new-query-to-the-query-suite).