chore: Adjust headline sizes (#131)

h4 and below were becoming really small, even smaller than the
normal paragraphs. This commit adds a linear scale from h2 to
h6.

Author: Techassi

src/css/doc.css

@@ -76,6 +76,28 @@
   font-weight: var(--alt-heading-font-weight);
 }
 
+/* Custom font sizes, because h4 and down were getting really small */
+
+.doc h2 {
+  font-size: 1.7rem;
+}
+
+.doc h3 {
+  font-size: 1.5rem;
+}
+
+.doc h4 {
+  font-size: 1.3rem;
+}
+
+.doc h5 {
+  font-size: 1.1rem;
+}
+
+.doc h6 {
+  font-size: 0.9rem;
+}
+
 .doc h1 code,
 .doc h2 code,
 .doc h3 code,