docs: how to construct the lecture URL (#133)

README.md

@@ -40,7 +40,7 @@ An educational web app for training program tracing skills.
    yarn start
    ```
 
-2. Open problems via the following URLs
+2. Open lectures via the following URLs:
    - 初級プログラミングⅠ
      1. http://localhost:3000/courses/tuBeginner1/lectures/8d692b48-8c19-4679-8d8f-3f27a051d44d
      2. http://localhost:3000/courses/tuBeginner1/lectures/d4de75e2-758b-4500-b38e-96213c360527
@@ -53,6 +53,13 @@ An educational web app for training program tracing skills.
    - 初級プログラミングⅡ
      1. http://localhost:3000/courses/tuBeginner2/lectures/5ba06885-2044-4c1e-bd65-2a9c5e9c9e39
 
+   The URL format is as follows.
+   You can find parameter values from `NEXT_PUBLIC_COURSE_ID_TO_LECTURE_IDS_JSON` in the `.env` file.
+
+   ```
+   http://localhost:3000/courses/[courseId]/lectures/[lectureId]
+   ```
+
 ### Change Database Schema
 
 1. Change `prisma/schema.prisma`