Adds release instructions

RELEASE.md

@@ -0,0 +1,92 @@
+# Steps to Release Bytewax
+
+## 1. One Final PR
+
+Make a PR which commits the following:
+
+1. Bumps version number in `Cargo.toml`
+
+   ```diff
+   *** Cargo.toml
+    [package]
+   -version = "0.1.0"
+   +version = "1.2.3"
+   ```
+
+2. Commits updated API docs
+
+   ```sh
+   (.venv) bytewax/apidocs $ pip install -r requirements.txt
+   (.venv) bytewax/apidocs $ rm -rf html/
+   (.venv) bytewax/apidocs $ ./build.sh
+   ```
+
+   You'll get a warning about `Couldn't read PEP-224 variable
+   docstrings`, but ignore that as our PyO3 Rust pyclasses don't have
+   Python source `pdoc` can read.
+
+   If we've been committing these as we go, there might not be any
+   changes to commit here. That's fine.
+
+3. Labels the latest changelog entries with the version number
+
+   Look in `CHANGELOG.md` for the latest batch of hand-written
+   changelog notes and add a new headings with the version number.
+
+   ```diff
+   *** CHANGELOG.md
+    ## Latest
+
+    __Add any extra change notes here and we'll put them in the release
+    notes on GitHub when we make a new release.__
+
+   +## 1.2.3
+   +
+    * Example note here. Describe any super important changes that you
+      wouldn't glean from PR names which will be added by GitHub
+      automatically.
+   ```
+
+Approve and merge that PR.
+
+## 2. Create Release on GitHub
+
+Go to the [create a new GitHub release page for our
+repo](https://github.com/bytewax/bytewax/releases/new).
+
+1. Choose a tag and enter a tag with the new version number `v1.2.3`.
+
+2. Click "Auto-generate release notes".
+
+   This will pre-populate the GitHub release notes with a list of
+   changes via PRs.
+
+3. Copy and paste any hand-written notes from the section of
+   [`CHANGELOG.md`](https://raw.githubusercontent.com/bytewax/bytewax/main/CHANGELOG.md)
+   with this version into a new section of the GitHub release
+   description at the top.
+
+   ```diff
+   +## Overview
+   +* Paste in the stuff in `CHANGELOG.md` here.
+   +
+    ## What's Changed
+    * List of PRs that were merged, but sometimes the names aren't helpful.
+   ```
+
+4. *Press "Publish release"!*
+
+   This should create a tag in our repo named `v1.2.3` and CI will
+   kick off building, running tests, and pushing the final package to
+   PyPI.
+
+   Check that the CI run completed on [our CI actions
+   page](https://github.com/bytewax/bytewax/actions/workflows/CI.yml).
+
+## 3. Double check PyPI
+
+Double check our [Bytewax PyPI
+page](https://pypi.org/project/bytewax/) to make sure that the new
+version of the package is there.
+
+I think we're done! Update this if we're not!