Convert all icons to CSS variables, add feed button next to tags heading

sass/_footnotes-list.scss

@@ -3,50 +3,4 @@
 		margin-block-start: 0;
 		margin-block-end: 0;
 	}
-
-	a[href*="#fr-"] {
-		--icon: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16'%3E%3Cpath d='M5 14a1 1 0 0 1-.707-.293l-4-4a1 1 0 0 1 0-1.414l4-4a1 1 0 1 1 1.414 1.414L3.414 8H12c1.117 0 2-.883 2-2s-.883-2-2-2c-.55 0-1-.45-1-1s.45-1 1-1c2.2 0 4 1.8 4 4s-1.8 4-4 4H3.414l2.293 2.293A1 1 0 0 1 5 14m0 0'/%3E%3C/svg%3E");
-		-webkit-user-select: none;
-		-webkit-mask-image: var(--icon);
-		display: inline-block;
-		vertical-align: -0.3125em;
-		mask-image: var(--icon);
-		mask-size: cover;
-		transition: var(--transition);
-		background-color: var(--fg-muted-4);
-		width: 1rem;
-		height: 1rem;
-		color: transparent;
-		user-select: none;
-
-		:root[dir*="rtl"] & {
-			transform: scaleX(-1);
-
-			&:active {
-				transform: scaleX(-1) var(--active);
-			}
-		}
-
-		&:hover {
-			background-color: var(--accent-color);
-		}
-
-		&:active {
-			transform: var(--active);
-		}
-	}
-
-	a + a[href*="#fr-"],
-	li:target a[href*="#fr-"] {
-		opacity: var(--dim-opacity);
-		background-color: var(--accent-color);
-
-		&:hover {
-			opacity: 1;
-		}
-	}
-
-	li:target a[href*="#fr-"] {
-		text-shadow: none;
-	}
 }