Add minor fixes (buttons, headers)

source/css/buttons.css

@@ -4,6 +4,7 @@
   margin-right: auto;
 }
 
+button,
 .button,
 a.button {
   position: relative;
@@ -24,16 +25,22 @@ a.button {
 
   .dark-theme & {
     background: var(--dark-background-secondary);
+    color: inherit;
   }
 
   /* variants */
 
   &.outline {
     background: transparent;
-    border-color: rgba(0, 0, 0, .2);
+    border-color: var(--light-background-secondary);
     box-shadow: none;
     padding: 8px 18px;
 
+    .dark-theme & {
+      border-color: var(--dark-background-secondary);
+      color: inherit;
+    }
+
     :hover {
       transform: none;
       box-shadow: none;

source/css/list.css

@@ -34,7 +34,7 @@
 
   &-title {
     font-size: 2.625rem;
-    margin: 0;
+    margin: 0 0 20px;
 
     @media (--phone) {
       font-size: 2rem;

source/css/main.css

@@ -35,6 +35,7 @@ body {
 h1, h2, h3, h4, h5, h6 {
   display: flex;
   align-items: center;
+  line-height: 1.43;
 }
 
 h1 {