Add Sebastian Heid to the foundational infrastructure team (BOSH)

I have expertise with Azure and want to help maintain the bosh-azure-cpi-release.

Author: s4heid

toc/working-groups/foundational-infrastructure.md

@@ -332,6 +332,8 @@ areas:
     github: lunaticomic-vc
   - name: Saumya Dudeja
     github: dudejas
+  - name: Sebastian Heid
+    github: s4heid
   repositories:
   - cloudfoundry/bbl-state-resource
   - cloudfoundry/bosh