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, 210 insertions, 0 deletions

diff --git a/docs/_includes/docs.css b/docs/_includes/docs.css
new file mode 100644
index 000000000..b1dbb1b08
--- /dev/null
+++ b/docs/_includes/docs.css
@@ -0,0 +1,210 @@
+:root {
+	--aside-width: 300px;
+}
+
+@font-face {
+	font-family: 'Open Sans';
+	font-style: normal;
+	font-weight: 300 800;
+	font-stretch: 100%;
+	font-display: swap;
+	src: url('{{ "/assets/fonts/OpenSans.woff2" | relative_url }}') format('woff2');
+	unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
+}
+
+/* layout */
+html, body {
+	overflow-x: hidden;
+}
+
+body {
+	font-family: "Open Sans", "Helvetica Neue", Helvetica, Arial, system-ui, sans-serif;
+	line-height: 1.5;
+	min-height: 100vh;
+}
+
+aside {
+	padding: 1rem;
+	width: var(--aside-width);
+	height: 100vh;
+	border-right: 1px solid black;
+	position: fixed;
+	top: 0;
+	left: 0;
+	margin-right: 1rem;
+}
+
+aside > nav.docs {
+	overflow-y: scroll;
+	max-height: 90vh;
+}
+
+aside > nav.docs > ul {
+	margin-bottom: 10rem; /* extra scroll space */
+}
+
+aside > nav.docs ul {
+	padding-left: 1rem;
+	margin-right: 1rem;
+}
+
+main {
+	margin-left: calc(var(--aside-width) + 50px);
+	max-width: 70vw;
+}
+
+img {
+	max-width: 100%;
+}
+
+section.search {
+	margin-top: 1rem;
+	border-bottom: 1px solid black;
+}
+
+div.nojs-search {
+	margin-bottom: 1rem;
+}
+
+nav.mobile-nav {
+	display: none;
+}
+
+nav.lang-dropdown {
+	display: none;
+}
+
+div.lang-dropdown:target nav {
+	padding: 0.2rem;
+	display: block;
+	border: 1px solid black;
+	border-radius: 6px;
+	position: absolute;
+	background-color: white;
+	z-index: 100;
+	text-wrap: nowrap;
+}
+
+div#mobile-language:target nav {
+	right: 0.2rem;
+}
+
+div.lang-dropdown:target nav a:hover {
+	background-color: silver;
+}
+
+div.lang-dropdown:target a.close {
+	display: block;
+	cursor: default;
+	position: fixed;
+	top: 0;
+	left: 0;
+	width: 100vw;
+	height: 100vh;
+	z-index: 99; /* just below language dropdown */
+}
+
+nav.lang-dropdown ul {
+	margin: 0;
+	padding: 0;
+	list-style-type: none;
+}
+
+/* mobile layout */
+
+@media (max-width: 1200px) {
+	aside {
+		display: none;
+	}
+
+	aside a.close {
+		display: block;
+	}
+
+	aside a.lang-btn {
+		display: none;
+	}
+
+	html:has(aside:target) {
+		overflow-y: hidden;
+	}
+
+	body:has(aside:target) > a.close {
+		display: block;
+		cursor: default;
+		position: fixed;
+		top: 0;
+		background-color: black;
+		opacity: 0.3;
+		width: 100vw;
+		height: 100vh;
+		z-index: 99; /* just below aside */
+	}
+
+	aside:target {
+		display: block;
+		position: fixed;
+		background-color: white;
+		z-index: 100;
+	}
+
+	main {
+		margin-left: 1rem;
+		max-width: 90vw;
+	}
+
+	nav.mobile-nav {
+		display: block;
+		border-bottom: 1px dashed black;
+	}
+
+	nav.mobile-nav > a.toggle-aside {
+		color: black;
+		-webkit-tap-highlight-color: transparent;
+	}
+
+	nav.mobile-nav > a.toggle-aside svg {
+		width: 2rem;
+		height: 2rem;
+	}
+}
+
+/* general styling */
+a {
+	text-decoration: none;
+	color: #00e;
+}
+
+a.close {
+	display: none;
+}
+
+aside a.close {
+	float: right;
+	color: #f00;
+	font-size: 24px;
+	position: relative;
+	bottom: 4px;
+}
+
+table, th, tr, td {
+	border: 1px solid black;
+	border-collapse: collapse;
+}
+
+th, tr, td {
+	padding: 0.3rem;
+}
+
+button.copy {
+	margin: 0.5rem;
+	float: right;
+}
+
+div.lang-dropdown {
+	float: right;
+}
+
+a.lang-btn {
+	color: black;
+}