Add pull_request_template - copied directly from bevy

Author: Multirious

.github/pull_request_template.md

@@ -0,0 +1,38 @@
+# Objective
+
+- Describe the objective or issue this PR addresses.
+- If you're fixing a specific issue, say "Fixes #X".
+
+## Solution
+
+- Describe the solution used to achieve the objective above.
+
+## Testing
+
+- Did you test these changes? If so, how?
+- Are there any parts that need more testing?
+- How can other people (reviewers) test your changes? Is there anything specific they need to know?
+- If relevant, what platforms did you test these changes on, and are there any important ones you can't test?
+
+---
+
+## Showcase
+
+> This section is optional. If this PR does not include a visual change or does not add a new feature, you can delete this section.
+
+- Help others understand the result of this PR by showcasing your awesome work!
+- If this PR adds a new feature or public API, consider adding a brief pseudo-code snippet of it in action
+- If this PR includes a visual change, consider adding a screenshot, GIF, or video
+  - If you want, you could even include a before/after comparison!
+- If the Migration Guide adequately covers the changes, you can delete this section
+
+While a showcase should aim to be brief and digestible, you can use a toggleable section to save space on longer showcases:
+
+<details>
+  <summary>Click to view showcase</summary>
+
+```rust
+println!("My super cool code.");
+```
+
+</details>