feat!: restructure erstie guide, expand

Expanded the erstie guide massively (added guide for each semester),
restructured to new URLs, added summaries details

index.md

@@ -11,11 +11,11 @@ hero:
       text: Summaries
       link: /summaries/
     - theme: alt
-      text: Erstie Guide
-      link: /ersties/
-#   image:
-#     src: /logo.svg
-#     alt: logo
+      text: ETH (Erstie) Guide
+      link: /guide/
+  image:
+    src: https://static.janishutz.com/logo.jpg
+    alt: logo
 #
 # features:
 #   - title: Feature A