Update PR template to include check for PR description, title and bac…

…kports (#4215) (#4223)

Signed-off-by: Mario Dominguez <mariodominguez@eprosima.com>
(cherry picked from commit dbbb465)

Co-authored-by: Mario Domínguez López <116071334+Mario-DL@users.noreply.github.com>

.github/pull_request_template.md

@@ -1,4 +1,5 @@
 <!-- Provide a general summary of your changes in the Title above -->
+<!-- It must be meaningful and coherent with the changes -->
 
 <!--
     If this PR is still a Work in Progress [WIP], please open it as DRAFT.
@@ -11,14 +12,15 @@
 ## Description
 <!--
     Describe changes in detail.
+    This includes depicting the context, use case or current behavior and describe the proposed changes.
     If several features/bug fixes are included with these changes, please consider opening separated pull requests.
 -->
 
 <!--
     In case of bug fixes, please provide the list of supported branches where this fix should be also merged.
     Please uncomment following line, adjusting the corresponding target branches for the backport.
 -->
-<!-- @Mergifyio backport 2.9.x 2.6.x 2.1.x -->
+<!-- @Mergifyio backport 2.12.x 2.11.x 2.10.x 2.6.x -->
 
 <!-- If an issue is already opened, please uncomment next line with the corresponding issue number. -->
 <!-- Fixes #(issue) -->
@@ -41,6 +43,7 @@
 
 ## Reviewer Checklist
 - [ ] The PR has a milestone assigned.
+- [ ] The title and description correctly express the PR's purpose.
 - [ ] Check contributor checklist is correct.
 - [ ] Check CI results: changes do not issue any warning.
 - [ ] Check CI results: failing tests are unrelated with the changes.