chore(ci): add PR template (#824)

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,27 @@
+<!--
+^^^ Summarize the changes done and why they were done above.
+
+By submitting this pull request, you certify that you have read the
+[CONTRIBUTING.md](https://github.com/TagStudioDev/TagStudio/blob/main/CONTRIBUTING.md).
+
+IMPORTANT FOR FEATURES: Please verify that a feature request or some other form
+of communication with maintainers was already conducted in terms of approving.
+
+Thank you for your eagerness to contribute!
+-->
+
+## Tasks Completed
+
+<!-- No requirements, just context for reviewers. -->
+
+- Tested on:
+  - [ ] Windows x86
+  - [ ] Windows ARM
+  - [ ] macOS x86
+  - [ ] macOS ARM
+  - [ ] Linux x86
+  - [ ] Linux ARM
+  <!-- If an unspecified platform was tested, please add it here! -->
+- Tested:
+  - [ ] Basic functionality
+  - [ ] PyInstaller executable