feat(docs): provide pull request template (#377)

## Description

Updated PR template

## Testing

<!-- Describe the testing done for this PR -->


## Checklist

- [ ] I have run the CI coverage report. Add the `run-coverage` label to
this PR to enable it.

Author: seemenkina

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,12 +1,83 @@
 ## Description
 
-<!-- Describe the changes made in this PR -->
+<!-- Provide a clear summary of the changes and motivation behind them. -->
+<!-- Link related issues using "Closes #123" or "Related to #456". -->
+
+## Changes
+
+<!-- List the key changes in this PR. -->
+
+-
 
 ## Testing
 
-<!-- Describe the testing done for this PR -->
+<!-- Describe how the changes were tested. -->
+<!-- Include any relevant test commands, scenarios, or edge cases covered. -->
+
+---
+
+## PR Lifecycle
+
+> [!IMPORTANT]
+> **Draft PRs** signal that work is still in progress and **will not trigger CI**.
+> Only mark your PR as **Ready for review** when you believe it is complete.
+> All CI checks **must pass** before requesting a review.
+
+## Code Guidelines
+
+Please keep the following in mind (see [CONTRIBUTING.md](../CONTRIBUTING.md) for full details):
+
+### Commits
+
+- Follow [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/) (`feat(rln):`, `fix(utils):`, `chore:`, etc.)
+- Use the appropriate scope: `rln`, `rln-cli`, `rln-wasm`, `utils`, `ci`
+- GPG-sign your commits
+
+### Error Handling
+
+- **No panics in library code.** Do not use `unwrap()`, `expect()`, or `panic!()`
+  in production paths inside `rln/src/` or `utils/src/`.
+  The only acceptable exception is an internal invariant that is statically guaranteed — and even then,
+  prefer returning an error.
+- Use the project's `thiserror`-based error types (`RLNError`, `ProtocolError`, `UtilsError`, etc.)
+  and propagate errors with `?`.
+- Provide context in error variants (e.g., `InsufficientData { expected, actual }`).
+- `unwrap()` is fine in **tests**.
+
+### Code Style
+
+- Run `cargo fmt --all -- --check` to verify formatting (CI enforces this on stable).
+- Group imports: std first, then external crates, then local modules (see `rustfmt.toml`).
+- Use `pub(crate)` for items that should not be part of the public API.
+- Apply `Zeroize` / `ZeroizeOnDrop` to any struct holding secret material.
+
+### Linting (mirrors CI)
+
+CI runs clippy across multiple crate/feature combinations. Run the relevant checks locally before pushing:
+
+```bash
+# Default features — workspace root (rln + utils)
+cargo clippy --all-targets --tests --release -- -D warnings
+
+# Stateless feature — from rln/
+cd rln && cargo clippy --all-targets --tests --release \
+  --features=stateless --no-default-features -- -D warnings
+
+# WASM target — from rln-wasm/
+cd rln-wasm && cargo clippy --target wasm32-unknown-unknown \
+  --tests --release -- -D warnings
+```
 
+At minimum, run the default-features check. If your changes touch `stateless` or `rln-wasm`, run those checks as well.
 
 ## Checklist
 
-- [ ] I have run the CI coverage report. Add the `run-coverage` label to this PR to enable it.
+- [ ] My PR title follows [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/) format
+- [ ] I have linked the related issue(s)
+- [ ] `cargo fmt --all -- --check` produces no changes
+- [ ] Clippy passes for all affected crate/feature combinations (see [Linting](#linting-mirrors-ci) above)
+- [ ] `make test` passes locally
+- [ ] No new `unwrap()` / `expect()` / `panic!()` in library code
+- [ ] New code includes appropriate tests (unit / integration / WASM where applicable)
+- [ ] I have run the CI coverage report — add the `run-coverage` label to enable it
+- [ ] All CI checks pass and the PR is marked **Ready for review**