Use viewport unit to scale base font size

Use rems for font sizes and margin/padding

css/base.css

@@ -1,5 +1,18 @@
 html {
   box-sizing: border-box;
+  line-height: 1.5;
+}
+
+@media screen and (min-width: 50rem) {
+  html {
+    font-size: 2vw;
+  }
+}
+
+@media screen and (min-width: 62.5rem) {
+  html {
+    font-size: 1.25rem;
+  }
 }
 
 body {
@@ -7,8 +20,6 @@ body {
   background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='4' height='4' viewBox='0 0 4 4'%3E%3Cpath fill='%23e0e0e0' fill-opacity='0.55' d='M1 3h1v1H1V3zm2-2h1v1H3V1z'%3E%3C/path%3E%3C/svg%3E");
   color: var(--color-near-black);
   font-family: var(--body-font-family);
-  font-size: 16px;
-  line-height: 1.5;
   margin: 0;
 }
 
@@ -25,6 +36,8 @@ h1,
 h2,
 h3,
 h4,
+h5,
+h6,
 figure,
 table,
 p,