Add GitHub contribution docs

Author: adewale

.github/ISSUE_TEMPLATE/bug-report.md

@@ -0,0 +1,17 @@
+---
+name: Bug report
+about: Report a problem with the site or runner
+title: "Bug: "
+labels: bug
+assignees: ""
+---
+
+## What happened?
+
+## Expected behavior
+
+## Page URL
+
+## Browser / environment
+
+## Additional details

.github/ISSUE_TEMPLATE/example-improvement.md

@@ -0,0 +1,19 @@
+---
+name: Example improvement
+about: Suggest a correction or improvement to an example
+title: "Improve example: "
+labels: example
+assignees: ""
+---
+
+## Example
+
+<!-- e.g. /examples/classes -->
+
+## Issue
+
+<!-- What is confusing, incorrect, or missing? -->
+
+## Suggested change
+
+<!-- Optional: propose wording or code/output changes. -->

.github/pull_request_template.md

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+## Summary
+
+<!-- What changed? -->
+
+## Verification
+
+- [ ] `make verify`
+- [ ] `scripts/check_example_migration_parity.py`
+- [ ] `scripts/format_examples.py --check`
+- [ ] `make verify-python-version VERSION=3.13`
+- [ ] `git diff --check`
+
+## Example changes
+
+If this changes examples:
+
+- [ ] Updated files under `src/example_sources/*.md`
+- [ ] Kept exactly one `:::program` block per example
+- [ ] Kept `:::cell` source/output deterministic and executable
+- [ ] Ran `make verify-examples`
+- [ ] Ran `make check-generated`

CONTRIBUTING.md

@@ -0,0 +1,71 @@
+# Contributing
+
+Thanks for helping improve Python By Example.
+
+## Editing examples
+
+Examples live in:
+
+```text
+src/example_sources/*.md
+```
+
+Each example has:
+
+- TOML frontmatter with `slug`, `title`, `section`, `summary`, and `doc_path`
+- exactly one `:::program` block with the full editable program
+- one or more `:::cell` blocks with prose, Python source, and expected output
+- optional `:::note` blocks
+
+Use `doc_path`, not full versioned Python docs URLs. The active docs version comes from:
+
+```text
+src/example_sources/manifest.toml
+```
+
+Do not edit generated files by hand:
+
+```text
+src/example_sources_data.py
+src/asset_manifest.py
+public/*.css/js fingerprinted copies
+```
+
+Regenerate them with:
+
+```bash
+make build
+```
+
+## Before opening a pull request
+
+Start the local Worker for browser-backed checks:
+
+```bash
+uv run --group workers pywrangler dev --port 9696
+```
+
+Then run:
+
+```bash
+make verify
+scripts/check_example_migration_parity.py
+scripts/format_examples.py --check
+make verify-python-version VERSION=3.13
+git diff --check
+```
+
+For example-only changes, also run:
+
+```bash
+make verify-examples
+make check-generated
+```
+
+## Style expectations
+
+- Keep examples compact and language-tour focused.
+- Prefer practical names and output that proves the concept.
+- Keep source/output cells executable and deterministic.
+- Do not add task-cookbook examples to the language tour.
+- Link to official Python 3.13 documentation through `doc_path`.

README.md

@@ -153,6 +153,10 @@ make deploy
 
 `make deploy` runs `make build` first, so embedded example data and cache fingerprints are regenerated before Wrangler deploys.
 
+## Contributing
+
+See `CONTRIBUTING.md` for pull request workflow, example editing rules, and verification commands.
+
 ## Updating examples or Python version
 
 Edit Markdown files under `src/example_sources/`.