Rollup merge of #86503 - ehuss:rustc.css-fonts, r=jyn514,GuillaumeGomez

Fix rust.css fonts.

The `rust.css` file (used for all non-rustdoc and non-mdbook pages) has gotten out of sync with rustdoc's css. The two share the same fonts, so this updates them to match what rustdoc uses.

It would be ideal not to need this at all, but that's for another time.

Author: JohnTitor

src/doc/rust.css

@@ -1,45 +1,68 @@
+/* See FiraSans-LICENSE.txt for the Fira Sans license. */
 @font-face {
 	font-family: 'Fira Sans';
 	font-style: normal;
 	font-weight: 400;
-	src: local('Fira Sans'), url("FiraSans-Regular.woff") format('woff');
+	src: local('Fira Sans'),
+		url("FiraSans-Regular.woff2") format("woff2"),
+		url("FiraSans-Regular.woff") format('woff');
 	font-display: swap;
 }
 @font-face {
 	font-family: 'Fira Sans';
 	font-style: normal;
 	font-weight: 500;
-	src: local('Fira Sans Medium'), url("FiraSans-Medium.woff") format('woff');
+	src: local('Fira Sans Medium'),
+		url("FiraSans-Medium.woff2") format("woff2"),
+		url("FiraSans-Medium.woff") format('woff');
 	font-display: swap;
 }
+
+/* See SourceSerif4-LICENSE.md for the Source Serif 4 license. */
 @font-face {
-	font-family: 'Source Serif Pro';
+	font-family: 'Source Serif 4';
 	font-style: normal;
 	font-weight: 400;
-	src: local('Source Serif Pro'), url("SourceSerifPro-Regular.ttf.woff") format('woff');
+	src: local('Source Serif 4'), url("SourceSerif4-Regular.ttf.woff") format('woff');
 	font-display: swap;
 }
 @font-face {
-	font-family: 'Source Serif Pro';
+	font-family: 'Source Serif 4';
 	font-style: italic;
 	font-weight: 400;
-	src: url("SourceSerifPro-It.ttf.woff") format('woff');
+	src: local('Source Serif 4 Italic'), url("SourceSerif4-It.ttf.woff") format('woff');
 	font-display: swap;
 }
 @font-face {
-	font-family: 'Source Serif Pro';
+	font-family: 'Source Serif 4';
 	font-style: normal;
 	font-weight: 700;
-	src: local('Source Serif Pro Bold'), url("SourceSerifPro-Bold.ttf.woff") format('woff');
+	src: local('Source Serif 4 Bold'), url("SourceSerif4-Bold.ttf.woff") format('woff');
 	font-display: swap;
 }
+
+/* See SourceCodePro-LICENSE.txt for the Source Code Pro license. */
 @font-face {
 	font-family: 'Source Code Pro';
 	font-style: normal;
 	font-weight: 400;
 	/* Avoid using locally installed font because bad versions are in circulation:
 	 * see https://github.com/rust-lang/rust/issues/24355 */
-	src: url("SourceCodePro-Regular.woff") format('woff');
+	src: url("SourceCodePro-Regular.ttf.woff") format('woff');
+	font-display: swap;
+}
+@font-face {
+	font-family: 'Source Code Pro';
+	font-style: italic;
+	font-weight: 400;
+	src: url("SourceCodePro-It.ttf.woff") format('woff');
+	font-display: swap;
+}
+@font-face {
+	font-family: 'Source Code Pro';
+	font-style: normal;
+	font-weight: 600;
+	src: url("SourceCodePro-Semibold.ttf.woff") format('woff');
 	font-display: swap;
 }
 
@@ -55,7 +78,7 @@ body {
 	background-color: white;
 	margin: 0 auto;
 	padding: 0 15px;
-	font-family: "Source Serif Pro", Georgia, Times, "Times New Roman", serif;
+	font-family: "Source Serif 4", Georgia, Times, "Times New Roman", serif;
 	font-size: 18px;
 	color: #333;
 	line-height: 1.428571429;