Increase impl items indent and decrease documentation indent for impl block

Author: GuillaumeGomez

src/librustdoc/html/static/css/rustdoc.css

@@ -36,6 +36,8 @@ xmlns="http://www.w3.org/2000/svg" fill="black" height="18px">\
 	--button-border-radius: 2px;
 	--toolbar-button-border-radius: 6px;
 	--code-block-border-radius: 6px;
+	--impl-items-indent: 0.5em;
+	--docblock-indent: 24px;
 }
 
 /* See FiraSans-LICENSE.txt for the Fira Sans license. */
@@ -908,7 +910,7 @@ both the code example and the line numbers, so we need to remove the radius in t
 .docblock h6 { font-size: 0.875rem; }
 
 .docblock {
-	margin-left: 24px;
+	margin-left: var(--docblock-indent);
 	position: relative;
 }
 
@@ -981,7 +983,11 @@ div.where {
 
 .item-info {
 	display: block;
-	margin-left: 24px;
+	margin-left: var(--docblock-indent);
+}
+.impl-items > .item-info {
+	/* Margin of docblocks + margin of impl block items. */
+	margin-left: calc(var(--docblock-indent) + var(--impl-items-indent));
 }
 
 .item-info code {
@@ -2154,6 +2160,15 @@ details.toggle > summary:not(.hideme)::before {
 	left: -24px;
 }
 
+/* We indent items of an impl block to have a visual marker that these items are part
+   of this impl block. */
+.impl-items > *:not(.item-info),
+/* We also indent the first top doc comment the same to still keep an indent on the
+   doc block while aligning it with the impl block items. */
+.implementors-toggle > .docblock {
+	margin-left: var(--impl-items-indent);
+}
+
 details.big-toggle > summary:not(.hideme)::before {
 	left: -34px;
 	top: 9px;
@@ -2448,8 +2463,11 @@ in src-script.js and main.js
 	}
 
 	/* Align summary-nested and unnested item-info gizmos. */
+	.item-info {
+		margin-left: 10px;
+	}
 	.impl-items > .item-info {
-		margin-left: 34px;
+		margin-left: 28px;
 	}
 
 	.src nav.sub {
@@ -2483,24 +2501,24 @@ in src-script.js and main.js
 }
 
 @media print {
+	:root {
+		--docblock-indent: 0;
+	}
+
 	nav.sidebar, nav.sub, .out-of-band, a.src, #copy-path,
 	details.toggle[open] > summary::before, details.toggle > summary::before,
 	details.toggle.top-doc > summary {
 		display: none;
 	}
 
-	.docblock {
-		margin-left: 0;
-	}
-
 	main {
 		padding: 10px;
 	}
 }
 
 @media (max-width: 464px) {
-	.docblock {
-		margin-left: 12px;
+	:root {
+		--docblock-indent: 12px;
 	}
 
 	.docblock code {