readme: add showcase screenshot

README.md

@@ -5,13 +5,15 @@ Supports all box sizes as long as they hold between 2 and 16 numbers, and has a
 Lets you pencil out the candidates as well, which is necessary for advanced techniques.
 Jigsaw (squiggly) puzzles are also supported, but manually entering them in CLI is annoying.
 
+![image](https://github.com/Ryp/sudoku-zig/assets/1625198/aeef8711-5366-4aad-886a-1e3bf295cd86)
+
 ## Running
 
 This should get you going after cloning the repo:
 ```sh
 zig build run -- 3 3 72..96..3...2.5....8...4.2........6.1.65.38.7.4........3.8...9....7.2...2..43..18
 ```
-NOTE: The sudoku string has to contain valid clue characters, anything else is considered as an empty cell.
+> **NOTE:** The sudoku string has to contain valid clue characters, anything else is considered as an empty cell.
 
 ![image](https://github.com/Ryp/sudoku-zig/assets/1625198/1e333afa-67a0-49b1-876a-8b180dd0b525)
 
@@ -45,6 +47,6 @@ zig build run -- 4 3 8.9....B.4C.C......3.B9...B5..A8.2...2.4..5........9.......
 ```sh
 zig build run -- 3 3 .38.4.1...6.9532......6....97......54..........5..2......6..8...57....6.34.8..... 111111222113444422133455442334455222366657777366559997366659977386858997888888997
 ```
-NOTE: Jigsaw puzzles need a second string that matches each cell with its associated region, so it's like the sudoku string but instead of clues you write the region index
+> **NOTE:** Jigsaw puzzles need a second string that matches each cell with its associated region, so it's like the sudoku string but instead of clues you write the region index
 
 ![image](https://github.com/Ryp/sudoku-zig/assets/1625198/5982b7f8-c556-40ea-bc1b-68583388342f)