rustdoc: improve stability mark arrows

src/librustdoc/html/static/rustdoc.css

@@ -542,11 +542,12 @@ h4 > code, h3 > code, .invisible > code {
 }
 
 .content .stability::before {
-	content: '˪';
-	font-size: 30px;
+	content: '⤶';
+	transform:rotate(90deg);
+	font-size: 25px;
 	position: absolute;
-	top: -9px;
-	left: -13px;
+	top: -6px;
+	left: -17px;
 }
 
 .content .impl-items .method, .content .impl-items > .type, .impl-items > .associatedconstant {

src/librustdoc/html/static/themes/dark.css

@@ -105,6 +105,8 @@ pre {
 .content .highlighted.primitive { background-color: #00708a; }
 .content .highlighted.keyword { background-color: #884719; }
 
+.content .stability::before { color: #ccc; }
+
 .content span.enum, .content a.enum, .block a.current.enum { color: #82b089; }
 .content span.struct, .content a.struct, .block a.current.struct { color: #2dbfb8; }
 .content span.type, .content a.type, .block a.current.type { color: #ff7f00; }

src/librustdoc/html/static/themes/light.css

@@ -105,6 +105,8 @@ pre {
 .content .highlighted.primitive { background-color: #9aecff; }
 .content .highlighted.keyword { background-color: #f99650; }
 
+.content .stability::before { color: #ccc; }
+
 .content span.enum, .content a.enum, .block a.current.enum { color: #508157; }
 .content span.struct, .content a.struct, .block a.current.struct { color: #ad448e; }
 .content span.type, .content a.type, .block a.current.type { color: #ba5d00; }