Improve layout of documentation page and add search feature (#8247)

* Improve layout of documentation page and add search feature

Closes https://github.com/FreshRSS/FreshRSS/issues/7915, https://github.com/FreshRSS/FreshRSS/issues/5325

Also: anchor headings and fix building site locally

* Further improvements

* Set color of hyperlinks
* Consistent styling of close aside button across devices
* Mobile layout 600px -> 1200px
* Add suffix to docs `<title>`
    * Note: titles of pages probably need to be improved, since currently they are just derived from the names of the first heading on every page
* Add favicon

* Improve font

* Try to fix favicon not loading correctly on GH pages

* Use local font

* Attempt to fix GH pages

* Final improvements

* Copy to clipboard button
* Support for nojs search
* Dark mode
* Load search.json (200KB json) only on search input focus
* Keep scroll state of sidebar across navigations

* Clickable images and CSP

CSP so we avoid hotlinking resources and clickable images are useful for zooming on mobile for example

* Fix typos

* Disable Dark Reader extension if dark mode CSS is loaded

* Support internationalisation (via language dropdown)

* Add Gemfile.lock

* Make CI build work with the custom plugin

* Make menus closable with Esc

* Fix typos CI

* Suggestions

* Use `ruby/setup-ruby` action in workflow for installing and caching gems.

* Run build only when there are changes to `docs/`

See: https://docs.github.com/en/actions/reference/workflows-and-actions/events-that-trigger-workflows?versionId=free-pro-team%40latest&productId=actions#running-your-workflow-only-when-a-push-to-specific-branches-occurs

* Change font to `Open Sans`

* Increase line height

* Fix Liquid syntax error

1 files changed, 63 insertions, 0 deletions

diff --git a/docs/assets/js/docs.js b/docs/assets/js/docs.js
new file mode 100644
index 000000000..c14fce920
--- /dev/null
+++ b/docs/assets/js/docs.js
@@ -0,0 +1,63 @@
+/* globals i18n */
+
+if (window.matchMedia('(prefers-color-scheme: dark)').matches) {
+	document.head.insertAdjacentHTML('beforeend', `
+	<meta name="darkreader-lock">
+	`);
+}
+
+let asideNav;
+
+window.addEventListener('beforeunload', () => {
+	sessionStorage.setItem('sidebar_scrollTop', asideNav.scrollTop);
+});
+
+window.addEventListener('keydown', (e) => {
+	if (e.key === 'Escape') {
+		location.hash = 'close';
+	}
+});
+
+document.addEventListener('DOMContentLoaded', () => {
+	asideNav = document.querySelector('aside > nav.docs');
+
+	const sidebar_scrollTop = sessionStorage.getItem('sidebar_scrollTop');
+	if (sidebar_scrollTop) {
+		asideNav.scrollTo(0, sidebar_scrollTop);
+		sessionStorage.removeItem('sidebar_scrollTop');
+	}
+
+	for (const el of document.querySelectorAll('div.highlight')) {
+		/* eslint-disable @stylistic/max-len */
+		el.insertAdjacentHTML('afterbegin', `
+		<button class="copy" title="${i18n.copy_to_clipboard}">
+			<svg xmlns="http://www.w3.org/2000/svg" width="16" height="16" fill="currentColor" viewBox="0 0 16 16">
+				<path d="M4 1.5H3a2 2 0 0 0-2 2V14a2 2 0 0 0 2 2h10a2 2 0 0 0 2-2V3.5a2 2 0 0 0-2-2h-1v1h1a1 1 0 0 1 1 1V14a1 1 0 0 1-1 1H3a1 1 0 0 1-1-1V3.5a1 1 0 0 1 1-1h1z"/>
+				<path d="M9.5 1a.5.5 0 0 1 .5.5v1a.5.5 0 0 1-.5.5h-3a.5.5 0 0 1-.5-.5v-1a.5.5 0 0 1 .5-.5zm-3-1A1.5 1.5 0 0 0 5 1.5v1A1.5 1.5 0 0 0 6.5 4h3A1.5 1.5 0 0 0 11 2.5v-1A1.5 1.5 0 0 0 9.5 0z"/>
+			</svg>
+		</button>
+		`);
+		/* eslint-enable @stylistic/max-len */
+		const copyBtn = el.querySelector('button.copy');
+		copyBtn.addEventListener('click', () => {
+			const snippet = el.querySelector('code').innerText;
+			if (navigator.clipboard) {
+				navigator.clipboard.writeText(snippet);
+			} else {
+				// Fallback if no HTTPS
+				const input = document.createElement('textarea');
+				input.innerHTML = snippet;
+				document.body.append(input);
+				input.select();
+				document.execCommand('copy');
+				input.remove();
+			}
+		});
+	}
+
+	for (const el of document.querySelectorAll('img')) {
+		if (el.parentNode.tagName !== 'A') {
+			el.outerHTML = `<a href="${el.getAttribute('src')}">${el.outerHTML}</a>`;
+		}
+	}
+});