expand the issue template for new lints

.github/ISSUE_TEMPLATE/new_lint.yml

@@ -48,3 +48,24 @@ body:
         ```
     validations:
       required: true
+  - type: textarea
+    id: comparison
+    attributes:
+      label: Comparision with existing lints
+      description: |
+        What makes this lint different from any existing lints that are similar, and how are those differences useful?
+
+        You can [use this playground template to see what existing lints are triggered by the bad code][playground]
+        (make sure to use "Tools > Clippy" and not "Build").
+        You can also look through the list of [rustc's allowed-by-default lints][allowed-by-default],
+        as those won't show up in the playground above.
+
+        [allowed-by-default]: https://doc.rust-lang.org/rustc/lints/listing/allowed-by-default.html
+
+        [playground]: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2024&code=%23%21%5Bwarn%28clippy%3A%3Apedantic%29%5D%0A%23%21%5Bwarn%28clippy%3A%3Anursery%29%5D%0A%23%21%5Bwarn%28clippy%3A%3Arestriction%29%5D%0A%23%21%5Bwarn%28clippy%3A%3Aall%29%5D%0A%23%21%5Ballow%28clippy%3A%3Ablanket_clippy_restriction_lints%2C+reason+%3D+%22testing+to+see+if+any+restriction+lints+match+given+code%22%29%5D%0A%0A%2F%2F%21+Template+that+can+be+used+to+see+what+clippy+lints+a+given+piece+of+code+would+trigger
+      placeholder: Unlike `clippy::...`, the proposed lint would...
+  - type: textarea
+    id: context
+    attributes:
+      label: Additional Context
+      description: Any additional context that you believe may be relevant.