minor symfony#60872 Update GitHub PR template (javiereguiluz, nicolas-grekas)

This PR was merged into the 6.4 branch.

Discussion
----------

Update GitHub PR template

| Q             | A
| ------------- | ---
| Branch?       | 6.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Issues        | -
| License       | MIT

Proposed changes:

  * Make some instructions more concise and actionable
  * Emphasize that PRs without a proper description are discouraged
  * Add a few emojis; not for decoration, but to improve visual separation and readability

Commits
-------

40bd9ab Update GitHub PR template

Author: nicolas-grekas

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,22 +1,25 @@
 | Q             | A
 | ------------- | ---
-| Branch?       | 7.4 for features / 6.4, 7.2, or 7.3 for bug fixes <!-- see below -->
+| Branch?       | 7.4 for features / 6.4, 7.2, or 7.3 for bug fixes
 | Bug fix?      | yes/no
-| New feature?  | yes/no <!-- please update src/**/CHANGELOG.md files -->
-| Deprecations? | yes/no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
-| Issues        | Fix #... <!-- prefix each issue number with "Fix #", no need to create an issue if none exists, explain below instead -->
+| New feature?  | yes/no <!-- if yes, also update src/**/CHANGELOG.md -->
+| Deprecations? | yes/no <!-- if yes, also update UPGRADE-*.md and src/**/CHANGELOG.md -->
+| Issues        | Fix #... <!-- prefix each issue number with "Fix #"; no need to create an issue if none exists, explain below -->
 | License       | MIT
 
 <!--
-Replace this notice by a description of your feature/bugfix.
-This will help reviewers and should be a good start for the documentation.
+🛠️ Replace this text with a concise explanation of your change:
+- What it does and why it's needed
+- A simple example of how it works (include PHP, YAML, etc.)
+- If it modifies existing behavior, include a before/after comparison
 
-Additionally (see https://symfony.com/releases):
- - Always add tests and ensure they pass.
- - Bug fixes must be submitted against the lowest maintained branch where they apply
-   (lowest branches are regularly merged to upper ones so they get the fixes too).
- - Features and deprecations must be submitted against the latest branch.
- - For new features, provide some code snippets to help understand usage.
- - Changelog entry should follow https://symfony.com/doc/current/contributing/code/conventions.html#writing-a-changelog-entry
- - Never break backward compatibility (see https://symfony.com/bc).
+Contributor guidelines:
+- ✅ Add tests and ensure they pass
+- 🐞 Bug fixes must target the **lowest maintained** branch where they apply
+  https://symfony.com/releases#maintained-symfony-branches
+- ✨ New features and deprecations must target the **feature** branch
+  and must add an entry to the changelog file of the patched component:
+  https://symfony.com/doc/current/contributing/code/conventions.html#writing-a-changelog-entry
+- 🔒 Do not break backward compatibility:
+  https://symfony.com/bc
 -->