fix(build): build package on merge to release/* branch (#185)

## Description
We should be building packages when commits are merged into the
`release/` branches, otherwise projects can get stuck waiting for
nightlies. Additionally, some packages like `rapids-dask-dependency`
don't get built in the nightly runs.

xref: rapidsai/build-planning#224

Author: gforsyth

.github/workflows/build.yaml

@@ -4,6 +4,7 @@ on:
   push:
     branches:
       - "main"
+      - "release/*"
     tags:
       - v[0-9][0-9].[0-9][0-9].[0-9][0-9]
   workflow_dispatch: