Update summary file

Author: thebracket

book/src/SUMMARY.md

@@ -76,5 +76,6 @@
     - [Logging](./chapter_71.md)
     - [Text Layers](./chapter_72.md)
     - [Systems/Dispatch](./chapter_73.md)
+    - [Dark Elf City 1](./chapter_74.md)
 - [Contributors](./contributors.md)
 - [Licensing](./license.md)