style: apply style guide fonts, colours, and readability fixes (#31)

## Summary

- Replaces custom "Vampyr" font with style guide fonts (Griffy, Kalam, Creepster, Henny Penny)
- Fixes illegible tagline, search placeholder, search results, shortcut badge, theme dropdown, and active sidebar item across light and dark modes
- Applies witchy code themes for light and dark mode
- Fixes invalid `env` language in code blocks (replaced with `sh`)
- Fixes invalid `message` aside icon in contact page (replaced with `star`)

✨ This PR was created with help from Hikari~ 🌸

Co-authored-by: Naomi Carrigan <commits@nhcarrigan.com>
Reviewed-on: #31
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

src/fonts/font-face.css

@@ -1,8 +1,22 @@
-@font-face {
-    font-family: "Vampyr";
-    src: url("https://cdn.nhcarrigan.com/fonts/vampyr.ttf") format("truetype");
+@import url('https://fonts.googleapis.com/css2?family=Kalam:wght@300;400;700&family=Creepster&family=Griffy&family=Henny+Penny&display=swap');
+
+body {
+    font-family: "Kalam", cursive !important;
 }
 
-* {
-    font-family: "Vampyr", monospace !important;
-}
+h1,
+h2,
+h3,
+h4,
+h5,
+h6 {
+    font-family: "Griffy", cursive !important;
+}
+
+.witchy-accent {
+    font-family: "Creepster", cursive;
+}
+
+.mystical-text {
+    font-family: "Henny Penny", cursive;
+}