improve the wording in the docs

docs/src/sources-sprites.md

@@ -55,7 +55,7 @@ martin --sprite /path/to/sprite_a --sprite /path/to/other/sprite_b
 ```
 
 To use generate Signed Distance Fields (SDFs) images instead, the `--make_sdf` Option can be added.
-This makes images be handled as a SDFs allowing their color to be set at runtime in the map redering engines.
+SDF-Images allow their color to be set at runtime in the map redering engine.
 
 ```bash
 martin --sprite /path/to/sprite_a --sprite  /path/to/other/sprite_b --make_sdf