Update PULL_REQUEST_TEMPLATE.md (#24311)

Update PR template:

- Mention list of PRs by recipe
- Simplify wording around testing locally
- request that PRs are motivated and detailed (what/why/how)

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,10 +1,15 @@
-Specify library name and version:  **lib/1.0**
 
-<!-- This is also a good place to share with all of us **why you are submitting this PR** (specially if it is a new addition to ConanCenter): is it a dependency of other libraries you want to package? Are you the author of the library? Thanks! -->
+### Summary
+Changes to recipe:  **lib/[version]**
 
+#### Motivation
+<!-- Please explain why this PR is needed, if it is a bugfix, please describe the bug or link to an existing issue. -->
+
+#### Details
+<!-- Explanation of the changes in the PR - this greatly simplifies the task of the reviewing team! -->
 
----
 
-- [ ] I've read the [contributing guidelines](https://github.com/conan-io/conan-center-index/blob/master/CONTRIBUTING.md).
-- [ ] I've used a [recent](https://github.com/conan-io/conan/releases/latest) Conan client version close to the [currently deployed](https://github.com/conan-io/conan-center-index/blob/master/.c3i/config_v1.yml#L6).
-- [ ] I've tried at least one configuration locally with the [conan-center hook](https://github.com/conan-io/hooks.git) activated.
+---
+- [ ] Read the [contributing guidelines](https://github.com/conan-io/conan-center-index/blob/master/CONTRIBUTING.md)
+- [ ] Checked that this PR is not a duplicate: [list of PRs by recipe](https://github.com/conan-io/conan-center-index/discussions/24240)
+- [ ] Tested locally with at least one configuration using a recent version of Conan