Add release instructions

Signed-off-by: Daniel Garnier-Moiroux <git@garnier.wf>

Author: Kehrlann

RELEASE.md

@@ -0,0 +1,73 @@
+# Release procedure
+
+## Off the `main` branch
+
+Instructions for a new major, new minor, or a patch when this would make it the latest version (e.g. 2.2.1 when latest version is 2.2.0)
+
+Ensure you have the latest changes locally, and no uncommitted changes:
+
+```shell
+git pull --ff-only
+git status
+```
+
+Set the version locally:
+
+```shell
+export RELEASE_VERSION=2.2.0
+export NEXT_VERSION=2.2.1-SNAPSHOT
+```
+
+Update the versions:
+
+```shell
+# Update version in pom
+./mvnw versions:set -DgenerateBackupPoms=false -DnewVersion=$RELEASE_VERSION
+```
+
+Update the docs (`docs/quickstart.md` and `mkdocs.yml`) to point to the new release version:
+
+```shell
+# "-i.bak" works with both GNU and BSD (macOS) sed, unlike a bare "-i".
+
+sed -i.bak \
+  -e "s|<version>[^<]*</version>|<version>${RELEASE_VERSION}</version>|g" \
+  -e "s|mcp-bom:[^\"]*\"|mcp-bom:${RELEASE_VERSION}\"|g" \
+  docs/quickstart.md
+rm docs/quickstart.md.bak
+
+sed -i.bak "s|\(mcp-core/\)[0-9][^ ]*|\1${RELEASE_VERSION}|" mkdocs.yml
+rm mkdocs.yml.bak
+```
+
+Commit everything and tag:
+
+```shell
+git add pom.xml mkdocs.yml docs/quickstart.md "**/pom.xml"
+git commit --signoff --message "Release version $RELEASE_VERSION"
+git tag --annotate "v$RELEASE_VERSION" --message "Release version $RELEASE_VERSION"
+```
+
+Review the commit and the tag (`git show "v$RELEASE_VERSION"`), then prepare the next version:
+
+```shell
+# Update version in pom
+./mvnw versions:set -DgenerateBackupPoms=false -DnewVersion=$NEXT_VERSION
+
+git add pom.xml "**/pom.xml"
+git commit --signoff --message "Next development version"
+```
+
+Review the commit (`git show`).
+
+> ⚠️ Take a good review before pushing!
+
+Then push it all:
+
+```shell
+git push --tags origin HEAD
+```
+
+Then release from the "[Release to Maven Central](https://github.com/modelcontextprotocol/java-sdk/actions/workflows/maven-central-release.yml)" action. Click "Run workflow", choose the newly pushed tag, then "run workflow".
+
+Create release notes.