💄 Replace css files with scss and factorize CSS rules

frontend/src/_utils.scss

@@ -0,0 +1,31 @@
+%transportMode {
+	aspect-ratio : 1 / 1;
+}
+
+%linePicto {
+	font-family: IDFVoyageur-bold;
+}
+
+%tramLinePicto {
+	@extend %linePicto;
+
+	aspect-ratio : 1 / 1;
+}
+
+%trainLinePicto {
+	@extend %linePicto;
+
+	aspect-ratio : 1 / 1;
+}
+
+%metroLinePicto {
+	@extend %linePicto;
+
+	aspect-ratio : 1 / 1;
+}
+
+%busLinePicto {
+	@extend %linePicto;
+
+	aspect-ratio : 2.25;
+}