fix: readd modal transitions

src/styles/common-imports.scss

@@ -16,6 +16,8 @@
 // since $tablet is defined by bulma we can just define it after importing the utilities
 $mobile: math.div($tablet, 2);
 
+@import "mixins";
+
 $family-sans-serif: 'Open Sans', Helvetica, Arial, sans-serif;
 $vikunja-font: 'Quicksand', sans-serif;