feat: generate dynamic docs header links

[ShubhamOulkar]

New design

light	dark

❌ design ❌

[netlify]

✅ Deploy Preview for expressjscom-preview ready!

Name	Link
🔨 Latest commit	2d3f972
🔍 Latest deploy log	https://app.netlify.com/projects/expressjscom-preview/deploys/68d36f9cb9117a000815e995
😎 Deploy Preview	https://deploy-preview-2055--expressjscom-preview.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[github-actions]

🚦 Lighthouse Results (Mobile & Desktop)

URL	Device	Perf	A11y	Best Practices
/	mobile	🔴 68	🟢 100	🟢 96
/en/blog/posts.html	mobile	🟠 78	🟢 96	🟢 96
/en/5x/api.html	mobile	🔴 66	🟢 95	🟢 96
/	desktop	🟢 100	🟢 100	🟢 96
/en/blog/posts.html	desktop	🟢 99	🟢 96	🟢 93
/en/5x/api.html	desktop	🟢 100	🟢 95	🟢 96

[jonchurch]

For some reason I thought we already had these, or had them in a PR, but I can't find any evidence for that.

Great idea.

Do note though, this will add these anchor links to h2, h3 on all pages of the site!

I didn't check all pages to see if it is messed up anywhere, but I caught some bugs on the docs page at least.

Is there a reason why this is living inside the copycode.js script file? it could move to the app.js file inside the jquery DOMContentLoaded callback at the top of the file

[jonchurch]

Suggested change

	for (const heading of headers) {
	for (const heading of headers) {
	if (h.querySelector('.heading-link')) continue;

Nit: A little paranoid but this will guard against the script running twice somehow by accident or hot reloading or something, preventing us from adding the elements twice.

[ShubhamOulkar]

I want thinking of implementing lazy attach links using IntersectionObserver or MutationObserver. WDYT?

Is there a reason why this is living inside the copycode.js script file?

Copy code and header link share same logic and needs asynchronous implementation.

[ShubhamOulkar]

I have addressed all reviews. Please take a look.

it could move to the app.js file inside the jquery

jQuery is migrated to web APIs

Do note though, this will add these anchor links to h2, h3 on all pages of the site!

Yes, this will add anchor on all pages. Here are some issues that are affecting this PR #2055 (comment) and #2056. First is fixed here itself, #2056 needs to be fixed.