Add info on secrets and signing keys to PROCESS.md

Author: philsttr

PROCESS.md

@@ -38,15 +38,18 @@ to the `master` branch that:
 2. Contains a commit message that starts with `[release]`
 
 The [build workflow](.github/workflows/build.yml) sees `[release]` in the commit message
-and uses the `maven-release-plugin` to perform the release.
-The `maven-release-plugin` strips the `-SNAPSHOT` from the pom version,
-performs the release, and bumps the version to the next `-SNAPSHOT` version.
-
-During the release process, the `nexus-staging-maven-plugin` deploys the artifact to
-a staging repository hosted at https://oss.sonatype.org/,
-and automatically [releases](https://central.sonatype.org/pages/releasing-the-deployment.html)
-the staging repository if no errors occur.
-After the staging repository is released, the new artifacts will eventually propagate to maven central.
+and uses the `maven-release-plugin` to perform the release, which then:
+
+1. Strips the `-SNAPSHOT` from the pom version,
+2. Creates the git tag, and builds the artifacts
+3. Uses the `maven-gpg-plugin` to sign the artifacts with [this GPG signing key](http://keyserver.ubuntu.com/pks/lookup?search=0x794038C5C4DF6A3F&fingerprint=on&op=index)
+   using the [`GPG_KEY` and `GPG_PASSPHRASE` secrets](https://github.com/logstash/logstash-logback-encoder/settings/secrets/actions)
+4. Uses the `nexus-staging-maven-plugin` to:
+   1. Deploy the artifact to a staging repository hosted at https://oss.sonatype.org/
+      using the [`OSSRH_USERNAME` and `OSSRH_PASSWORD` secrets](https://github.com/logstash/logstash-logback-encoder/settings/secrets/actions)
+   2. Automatically [release](https://central.sonatype.org/pages/releasing-the-deployment.html) the staging repository if no errors occur.
+      * After the staging repository is released, the new artifacts will eventually propagate to maven central. 
+5. Bumps the version to the next `-SNAPSHOT` version.
 
 After releasing, create a [release](https://github.com/logstash/logstash-logback-encoder/releases) for the tag
 that includes release notes of all the changes in the new version.