fix: fixes the ambient declarations on import (#429)

🎉 Thanks for sending this pull request! 🎉

Please make sure the title is clear and descriptive.

If you are fixing a typo or documentation, please skip these
instructions.

Otherwise please fill in the sections below.

**Which problem is this pull request solving?**

Example: I'm always frustrated when [...]

**List other issues or pull requests related to this problem**

Example: This fixes #5012

**Describe the solution you've chosen**

Example: I've fixed this by [...]

**Describe alternatives you've considered**

Example: Another solution would be [...]

**Checklist**

Please add a `x` inside each checkbox:

- [ ] I have read the [contribution
guidelines](../blob/master/CONTRIBUTING.md).
- [ ] The status checks are successful (continuous integration). Those
can be seen below.

src/main.ts

@@ -1,4 +1,11 @@
+import type { getNetlifyGlobal } from '@netlify/serverless-functions-api'
+
 export { builder } from './lib/builder.js'
 export { schedule } from './lib/schedule.js'
 export { stream } from './lib/stream.js'
 export * from './function/index.js'
+
+// Ambient type declarations
+declare global {
+  const Netlify: ReturnType<typeof getNetlifyGlobal>
+}