bump next version in sources during release

[feloy]

A release action is triggered when a tag is created.

During this action, a PR should be created, to be merged on main, to bump the Version var in pkg/version/version.go. For example when the release tag is v0.4.0, the version to be merged in main is 0.5.0-next)

Specialized tool can be used to get next version (use commit instead of latest when fetching module):

      - name: Install svu
        run: go install github.com/caarlos0/svu@latest

      - name: Generate next version tag
        id: tag
        run: |
          NEXT_VERSION=$(svu next)
          echo "next_version=$NEXT_VERSION" >> $GITHUB_OUTPUT
          git tag "$NEXT_VERSION"
          git push origin "$NEXT_VERSION"