Make PR template mention that PR titles will be used in release notes

Author: stefanhaller

.github/pull_request_template.md

@@ -11,6 +11,8 @@
 * [ ] You've read through your own file changes for silly mistakes etc
 
 <!--
-Be sure to name your PR with an imperative e.g. 'Add worktrees view'
+Be sure to name your PR with an imperative e.g. 'Add worktrees view', and make sure the title
+is suitable to be included as a bullet point in release notes (i.e. phrased from a user's point
+of view).
 see https://github.com/jesseduffield/lazygit/releases/tag/v0.40.0 for examples
 -->