DEV: Add body to created GitHub release (#1985)

PR fixes that new GitHub releases were lacking a body, where this was due to the fact that we were not outputting `tag_body` to `$GITHUB_ENV` so that it wasn't available in follow-up steps. However, because the body is a multiline string, we've got to wrap it in special syntax to get it to work (see [docs](https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#example-of-a-multiline-string) for example).

See https://github.com/py-pdf/pypdf/actions/runs/5601580443/jobs/10245662760?pr=1985 as an example test run that shows it working in a test workflow.

Closes #1971

.github/workflows/release.yaml

@@ -46,7 +46,10 @@ jobs:
  latest_tag=$(git describe --tags --abbrev=0)
  echo "latest_tag=$(git describe --tags --abbrev=0)" >> "$GITHUB_ENV"
  echo "date=$(date +'%Y-%m-%d')" >> "$GITHUB_ENV"
- tag_body=$(git tag -l "${latest_tag}" --format='%(contents:body)')
+ EOF=$(dd if=/dev/urandom bs=15 count=1 status=none | base64)
+ echo "tag_body<<$EOF" >> "$GITHUB_ENV"
+ git tag -l "${latest_tag}" --format='%(contents:body)' >> "$GITHUB_ENV"
+ echo "$EOF" >> "$GITHUB_ENV"
  - name: Create GitHub Release 🚀
  uses: actions/create-release@v1
  env:
@@ -56,4 +59,4 @@ jobs:
  release_name: Version ${{ env.latest_tag }}, ${{ env.date }}
  draft: false
  prerelease: false
- body: Body is ${{ env.tag_body }}
+ body: ${{ env.tag_body }}