bump(deps): update dependency rehype-slug to ^5.1.0 (#231)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [rehype-slug](https://togithub.com/rehypejs/rehype-slug) | [`^5.0.1`
-> `^5.1.0`](https://renovatebot.com/diffs/npm/rehype-slug/5.0.1/5.1.0)
|
[![age](https://badges.renovateapi.com/packages/npm/rehype-slug/5.1.0/age-slim)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://badges.renovateapi.com/packages/npm/rehype-slug/5.1.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://badges.renovateapi.com/packages/npm/rehype-slug/5.1.0/compatibility-slim/5.0.1)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://badges.renovateapi.com/packages/npm/rehype-slug/5.1.0/confidence-slim/5.0.1)](https://docs.renovatebot.com/merge-confidence/)
|

---

### Release Notes

<details>
<summary>rehypejs/rehype-slug</summary>

###
[`v5.1.0`](https://togithub.com/rehypejs/rehype-slug/releases/tag/5.1.0)

[Compare
Source](https://togithub.com/rehypejs/rehype-slug/compare/5.0.1...5.1.0)

- [`899b3b7`](https://togithub.com/rehypejs/rehype-slug/commit/899b3b7)
Add `options.prefix`
by [@&#8203;onyxcodes](https://togithub.com/onyxcodes) in
[https://github.com/rehypejs/rehype-slug/pull/15](https://togithub.com/rehypejs/rehype-slug/pull/15)

**Full Changelog**:
rehypejs/rehype-slug@5.0.1...5.1.0

</details>

---

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packages/contented-pipeline-md/package.json

@@ -37,7 +37,7 @@
     "rehype-autolink-headings": "^6.1.1",
     "rehype-external-links": "^2.0.1",
     "rehype-parse": "^8.0.4",
-    "rehype-slug": "^5.0.1",
+    "rehype-slug": "^5.1.0",
     "rehype-stringify": "^9.0.3",
     "remark-directive": "^2.0.1",
     "remark-directive-rehype": "^0.4.2",