docs: 📝 switch readme to markdown

README.md

@@ -2,6 +2,9 @@ Please add your content into the section folder. It should have the following st
 
 (obviously, you should replase sections and subsectionX with the section name and the subsection name)
 
+```bash
+$ tree OCRudoku-first-defense/
+
 OCRudoku-first-defense/
 ├── main.txt
 ├── README.txt
@@ -12,4 +15,5 @@ OCRudoku-first-defense/
         ├── subsection1
         │   └── subsection2.tex
         └── subsection2
-            └── subsection2.tex
+            └── subsection2.tex
+```