update README with syntax highlighting

README.md

@@ -6,7 +6,7 @@
 
 1. Put Pixel
 
-```
+```c
 void put_pixel(unsigned int x, unsigned int y, uint32_t color);
 ```
 
@@ -14,7 +14,7 @@ void put_pixel(unsigned int x, unsigned int y, uint32_t color);
 
 2. Clear Framebuffer
 
-```
+```c
 void clear_framebuffer(uint32_t color);
 ```
 
@@ -24,7 +24,7 @@ void clear_framebuffer(uint32_t color);
 
 The main function of a program that uses this engine should look something like this:
 
-```
+```c
 int main() {
 	// initialize the engine
 	if (engine_init(
@@ -50,7 +50,7 @@ Updating the framebuffer means changing color values in the respective struct an
 
 An excerpt from the main game loop is below:
 
-```
+```c
 ...
 
 // main game loop