Improve heading 3 and heading 4 styles for better visual hierarchy

- Add proper sizing and font weights to h3-h6 headings
- H3: text-xl (20px) + font-semibold for clear section breaks
- H4: text-lg (18px) + font-medium for subsections
- H5: text-base (16px) + font-medium for minor headings
- H6: text-sm (14px) + font-medium for smallest headings
- Consolidate duplicate h1 rules into single declaration
- Maintain existing h1 and h2 styling that works well

Fixes issue where h3 and h4 headings didn't look like proper headings on the site.

Author: mich-elle-luna

assets/css/index.css

@@ -23,18 +23,30 @@ section.prose {
   @apply font-geist
 }
 
-.prose h1,
-.prose h3,
-.prose h4,
-.prose h5,
-.prose h6 {
-  @apply font-normal;
+.prose h1 {
+  @apply text-4xl font-normal break-words;
 }
 
 .prose h2 {
   @apply text-lg font-medium pb-3 border-b border-b-redis-pen-700 border-opacity-50;
 }
 
+.prose h3 {
+  @apply text-xl font-semibold;
+}
+
+.prose h4 {
+  @apply text-lg font-medium;
+}
+
+.prose h5 {
+  @apply text-base font-medium;
+}
+
+.prose h6 {
+  @apply text-sm font-medium;
+}
+
 .prose p, .prose ol, .prose ul {
   @apply text-base;
 }
@@ -47,10 +59,6 @@ section.prose {
   @apply bg-none font-monogeist;
 }
 
-.prose h1 {
-  @apply text-4xl break-words;
-}
-
 .prose h1[id],
 .prose h2[id],
 .prose h3[id],