docs: addding release notes (#2001)

Signed-off-by: Alyssa Wilk <[email protected]>

RELEASE.md

@@ -0,0 +1,27 @@
+# Release Process
+
+## Active development
+
+Active development is happening on the `main` branch, and a new versions will
+be released on major development milestones and/or following upstream Envoy
+releases.
+
+## Cutting a release
+
+* Update the [release notes](docs/root/intro/version_history.rst).
+  * Add a new `Pending Release` section with `Bugfixes:` and `Features:` section at the top of the file.
+  * Update the old `Pending Release` section with the release version and release date.
+  * Make sure all changes since the last release (``git log `git rev-list --tags --max-count=1`..HEAD``) are reflected in the current release.
+  * If building the quarterly release, also note the Envoy tagged release (e.g. as done in the [0.4.5](https://github.com/envoyproxy/envoy-mobile/pull/2000/files#diff-02cdc1a64b58714360c0cbdf245da06616364b110af4acd72ca364a524021eedR10) release
+* If building the quarterly release, ensure the Envoy checkout points to the latest [envoy tagged release](https://github.com/envoyproxy/envoy/tags)
+* Bump the version in [EnvoyMobile.podspec](EnvoyMobile.podspec) and [VERSION](VERSION) files
+* Create a PR with the above changes, get it approved and merged
+* Optionally, wait for CI to pass on main
+* Draft a new release
+  [here](https://github.com/envoyproxy/envoy-mobile/releases). Copy in the release notes you just created and publish it.
+* Wait for the [artifacts run](https://github.com/envoyproxy/envoy-mobile/actions/workflows/artifacts.yml)
+  for the tag release to finish running. Click on the workflow run to find the
+  generated artifacts (e.g.  [this](https://github.com/envoyproxy/envoy-mobile/actions/runs/1638634901)).
+  Download `envoy_android_aar_sources`, `envoy_ios_cocoapods`, and `envoy_ios_framework`.
+* Go back to your tagged release, edit the release, and upload the 3 files from
+  the previous step.