Add B.Schaffl by sjaehn

[kmturley]

Summary

• Adds B.Schaffl, a slider/shape-controlled MIDI velocity amplification and time-stretch plugin for producing swing/shuffle grooves.
• GPL-3.0. type: generator. Dropped a redundant .zip duplicate of the .tar.xz (verified identical content, same 46 files).

Test plan

• npx tsx src/validate.ts src/plugins/sjaehn/bschaffl/1.4.10/index.yaml passes

[github-actions]

VirusTotal Report:

• test/downloads/sjaehn/bschaffl/1.4.10/0-BSchaffl-1.4.10-linux-amd64.lv2.tar.xz

[github-actions]

Destination urls:
Registry: https://open-audio-stack.github.io/open-audio-stack-registry/plugins/sjaehn/bschaffl
Site: https://studiorack.github.io/studiorack-site/plugins/sjaehn/bschaffl

[github-actions]

Plugin author notification:

@sjaehn — your plugin has been submitted to the Open Audio Stack registry. Please review this PR and let us know if the metadata (name, description, tags, files) is correct. To see a full list of all currently added plugins, click here.