lesson 25 remaining grammar; theme lessons

docs/index.md

@@ -9,6 +9,10 @@ hero:
 
 [Sound Rules](./ภาษาเกาหลีเรียนง่าย/1/04-sound-rules.md)
 
+## [Themes](./howtostudykorean/theme/index.md)
+
+## Unit 1
+
 - [Lesson 1: Basic Sentences](./howtostudykorean/unit-1/01-sentences.md)
 - [Lesson 2: Particles](./howtostudykorean/unit-1/02-particles.md)
 - [Lesson 3: Verbs/Adjectives](./howtostudykorean/unit-1/03-verbs.md)