ci(release): publish RELEASE.md as the release body

Matches fleetbase/fleetbase, which has always used body_path. The release workflow now
requires RELEASE.md and refuses to tag without it, so without this the notes would be
mandatory to write and displayed nowhere.

generate_release_notes stays on so GitHub's commit list is appended beneath the
hand-written notes.

Author: roncodes

.github/workflows/create-release.yml

@@ -14,8 +14,9 @@ jobs:
           with:
             tag_name: ${{ github.ref_name }}
             name: ${{ github.ref_name }}
-            generate_release_notes: true 
+            body_path: RELEASE.md
+            generate_release_notes: true
             draft: false
             prerelease: false
           env:
-            GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+            GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}