Add ISSUE_TEMPLATE.md and PULL_REQUEST_TEMPLATE.md

Author: federicobucchi

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,20 @@
+### Expected behavior
+_[what you expected to happen]_
+
+### Actual behavior
+_[what actually happened]_
+
+### Steps to reproduce
+
+1. ...
+2. ...
+
+### If possible, minimal yet complete reproducer code (or URL to code)
+
+_[anything to help us reproducing the issue]_
+
+### SwiftMetrics version/commit hash
+
+_[the SwiftMetrics tag/commit hash]_
+
+### Swift & OS version (output of `swift --version && uname -a`)

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,13 @@
+_[One line description of your change]_
+
+### Motivation:
+
+_[Explain here the context, and why you're making that change. What is the problem you're trying to solve.]_
+
+### Modifications:
+
+_[Describe the modifications you've done.]_
+
+### Result:
+
+_[After your change, what will change.]_

Documentation/Contributing.md

@@ -257,8 +257,9 @@ $> Utilities/Docker/docker-utils swift-run # to run swift-run in the container
 7. Commit (include the Radar link or JIRA issue id in the commit message if possible and a description your changes). Try to have only 1 commit in your PR (but, of course, if you add changes that can be helpful to be kept aside from the previous commit, make a new commit for them).
 8. Push the commit / branch to your fork
 9. Make a PR from your fork / branch to `apple: main`
-10. Reviewers are going to be automatically added to your PR
-11. Merge pull request when you received approval from the reviewers (one or more)
+10. While creating your PR, make sure to add one of the [PR Templates](https://github.com/apple/swift-package-manager/tree/main/.github) in your PR message depending on the reasoning of your PR.
+11. Reviewers are going to be automatically added to your PR
+12. Merge pull request when you received approval from the reviewers (one or more)
 
 ## Using Continuous Integration
 SwiftPM uses [swift-ci](https://ci.swift.org) infrastructure for its continuous integration testing. The bots can be triggered on pull-requests if you have commit access. Otherwise, ask