Bump bl from 3.0.0 to 3.0.1 in /plugins/gatsby-plugin-ghost-manifest

Bumps [bl](https://github.com/rvagg/bl) from 3.0.0 to 3.0.1.
- [Release notes](https://github.com/rvagg/bl/releases)
- [Commits](rvagg/bl@v3.0.0...v3.0.1)

Signed-off-by: dependabot[bot] <[email protected]>