added release instructions

RELEASE.md

@@ -0,0 +1,21 @@
+# Release process
+
+## Git
+1. Make sure you are on `main` branch:
+    ```
+    git checkout main
+    ```
+1. Verify, that `CHANGELOG.md` contains all the changes for the release.
+1. Create a tag and push to origin:
+    ```
+    git tag v0.0.1
+    git push origin --tags
+    ```
+
+## GitHub
+
+1. Click the [Create a new release](https://github.com/Teradata/dbt-teradata-utils/releases/new) link on the project homepage in GitHub
+1. Type `v{semantic_version}` as the "tag version" (e.g., `v0.0.1`)
+1. Leave the "target" as `main`
+1. Type `dbt-teradata-utils {semantic_version}` as the "release title" (e.g. `dbt-teradata-utils 0.0.1`)
+1. Click the "publish release" button