implement game configuration file

this integrates https://github.com/cktan/tomlc99 into the repo as a dependency

src/twn_engine_context_c.h

@@ -8,6 +8,7 @@
 #include "rendering/twn_rendering_c.h"
 
 #include <SDL2/SDL.h>
+#include <toml.h>
 
 #include <stdbool.h>
 #include <stdint.h>
@@ -21,11 +22,24 @@ typedef struct EngineContext {
     int argc;
     char **argv;
 
-    struct Primitive2D *render_queue_2d;
+    /* configuration */
+    toml_table_t *config_table;
+    int64_t base_render_width;
+    int64_t base_render_height;
+    int64_t ticks_per_second;
+    int64_t keybind_slots;
+    int64_t texture_atlas_size;
+    int64_t font_texture_size;
+    int64_t font_oversampling;
+    TextureFilter font_filtering;
+
+    /* rendering */
+    Primitive2D *render_queue_2d;
     MeshBatchItem *uncolored_mesh_batches;
-    struct TextCache text_cache;
+    TextCache text_cache;
     TextureCache texture_cache;
 
+    /* audio */
     AudioChannelItem *audio_channels;
     SDL_AudioDeviceID audio_device;
     int audio_stream_frequency;