feat: add ci, testing and base structure

tests/test_linear_algebra.c

@@ -0,0 +1,12 @@
+#include <assert.h>
+#include "curtle/linear_algebra.h"
+
+int main() {
+    vec2 a = {1,2};
+    vec2 b = {3,4};
+
+    vec2 r = vec2_add(a,b);
+
+    assert(r.x == 4);
+    assert(r.y == 6);
+}