add missing imports to root README snippets

[ambikeesshh]

Problem

The Multi-tenancy and Webhooks examples in the root README.md use createCorsair, plugin factories, and processWebhook without imports.

Fix

Add the imports those snippets need so a reader can copy them without guessing package names.

Touch

• README.md (Multi-tenancy + Webhooks sections)

Done when

• multi-tenancy snippet has imports
• webhooks snippet has imports
• no unused or fake imports

Verify

Skim both sections and check each typescript fence for imports.

[tomatotomata]

I can take this documentation fix. I will trace the exported helper and plugin-factory names, add only the imports each TypeScript example actually uses, and verify both fences for unused or invented imports before opening a PR. Let me know what you think.