Include temporary feature freeze in templates

Author: blyxyas

.github/ISSUE_TEMPLATE/new_lint.yml

@@ -1,5 +1,7 @@
 name: New lint suggestion
-description: Suggest a new Clippy lint.
+description: |
+  Suggest a new Clippy lint (currently not accepting new lints)
+  Check out the Clippy book for more information about the feature freeze.
 labels: ["A-lint"]
 body:
   - type: markdown

.github/PULL_REQUEST_TEMPLATE.md

@@ -32,6 +32,10 @@ order to get feedback.
 
 Delete this line and everything above before opening your PR.
 
+Note taht we are currently not taking in new PRs that add new lints. We are in a
+feature freeze. Check out the book for more information. If you open a
+feature-adding pull request, its review will be delayed.
+
 ---
 
 *Please write a short comment explaining your change (or "none" for internal only changes)*