contributing: add info in the readme, add a pr template

Signed-off-by: Gunwant Jain <mail@wantguns.dev>

.github/pull_request_template.md

@@ -0,0 +1,18 @@
+---
+
+Thanks for taking the time !
+
+Please ensure that some basic checks are passed before creating this Pull Request:
+
+- [ ] Cargo Format
+    - Run `cargo fmt` on the project.
+    
+- [ ] Clippy lints
+    - Run `cargo clippy -- -Dwarnings` on the project to check for suggestions
+    - Run `cargo clippy --fix` to let clippy apply the suggestions itself, if any.
+
+This can be tiresome for frequent contributors, so it might would be better if
+you used a git pre-push hook as mentioned in the [readme](readme.md#hacking).
+
+The [Build CI](.github/workflow/buildci.yaml) will also check whether the project can be compiled and
+cross-compiled to arm64 without any errors.