Fix missing sdl3game.pc for pkg-config, change sprite speed and character movement values to long int expressed in nanoseconds for better compatibility with SDL_Time and locking against game clock, still expressed as milliseconds in json

include/sdl3game/character.h

@@ -13,7 +13,7 @@ typedef struct character {
   SDL_PropertiesID state_sprites;
   akerr_ErrorContext AKERR_NOIGNORE *(*sprite_add)(struct character *, sprite *, int);
   akerr_ErrorContext AKERR_NOIGNORE *(*sprite_get)(struct character *, int, sprite **);
-  int movementspeed;
+  long int movementspeed;
   float vx;
   float vy;
 } character;