Add pull request template (#17)

.github/pull_request_template.md

@@ -0,0 +1,15 @@
+# Technology Radar Pull Request Template
+
+When making a pull request, please ensure that the following
+things are done.
+
+- [ ] I've added a short description of the entry that
+      clarifies what it does and why it's useful
+- [ ] I've added links to the entry's documentation and/or
+      website
+- [ ] My frontmatter is correct, complete and follows the
+      format specified in the [README](../README.md)
+- [ ] In case the entry is in the `adopt` category: I've
+      added at least one reference to showcase the entry usage
+      among our organization
+- [ ] I've described at least one use case for the entry