ci(release): fix the tarball staging path for LICENSE.txt (#128)

The release workflow copied `LICENSE`, but the file is `LICENSE.txt`, so `make release` for v0.12.0 died at the staging step and published nothing. Adds UPGRADING.md to the tarball while we're here.

Co-authored-by: django23 <827397+django23@users.noreply.github.com>

Author: django23

.github/workflows/release.yml

@@ -42,7 +42,7 @@ jobs:
           # asimov-<version>/{bin,lib,data} and installs with scripts/install.sh.
           STAGE="asimov-${FULL_VERSION}"
           mkdir -p "$STAGE"
-          cp -a bin lib data scripts LICENSE README.md CHANGELOG.md \
+          cp -a bin lib data scripts LICENSE.txt README.md CHANGELOG.md UPGRADING.md \
             com.stevegrunwell.asimov.plist "$STAGE/"
           TARBALL="${STAGE}.tar.gz"
           tar -czf "$TARBALL" "$STAGE"