docs: add contributing, git, and styleguide docs (#56)

CHANGELOG.md

@@ -0,0 +1,9 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres
+to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]

README.md

@@ -22,6 +22,13 @@ To interactivly choose what to run:
 just
 ```
 
+To format code:
+
+```bash
+just fmt
+```
+
+
 ## Prebuilt RocksDB
 
 By default, we compile RocksDB (a C++ project) from source during the build.
@@ -49,3 +56,4 @@ git checkout v8.10.0
 make -j 10 static_lib
 export ROCKSDB_LIB_DIR=/path/to/rocksdb
 ```
+

docs/contributing.md

@@ -0,0 +1,32 @@
+## Pull Requests
+
+All contributions to `tycho` are made via Pull Requests (PRs). Please follow
+these steps when creating a PR:
+
+- **Fork the Repository:** Fork the repository or create a new branch in the
+  repository if you have write access.
+- **Commit Structure:** We review each commit separately, and we do not use the
+  squash-merge strategy. Please manually combine any fixup commits before
+  sending them for review. Each commit should ideally focus on a single task.
+  For example, if you need to refactor a function to add a new feature cleanly,
+  place the refactoring in one commit and the new feature in another. If the
+  refactoring itself consists of many parts, separate these into individual
+  commits. Include tests and documentation in the same commit as the code they
+  test and document. The commit message should describe the changes in the
+  commit; the PR description can be brief or even empty, but feel free to
+  include a personal message.
+- **Testing:** Ensure that the changes are thoroughly tested. If the PR
+  introduces a new feature, it should also contain tests for that feature.
+- **Draft PRs:** Feel free to submit draft PRs to get early feedback and to
+  ensure you are on the right track.
+- **Commit Naming Convention:** Each commit should follow [Conventional
+  Commits](https://www.conventionalcommits.org/en/v1.0.0/). This helps us
+  automatically generate changelogs and version bumps. (todo: implement this)
+- **Documentation of Changes:** If your PR introduces a user-observable change (
+  e.g., a new protocol feature, new configuration option, new Prometheus metric,
+  etc.), please document it in [CHANGELOG.md](../CHANGELOG.md) in
+  the `[unreleased]` section.
+- **No Merge Policy:** The tycho repository uses
+  a [no merge policy](./git.md#no-merge-policy). Please rebase your branch on
+  top of the `master` branch before creating a PR.
+