feat: add floats

tests/float_unary.test

@@ -0,0 +1,21 @@
+[code]
+fn negate_f32(x: f32) -> f32 {
+    return -x;
+}
+
+fn negate_f64(x: f64) -> f64 {
+    return -x;
+}
+
+[harness]
+extern float negate_f32(float x);
+extern double negate_f64(double x);
+
+int main() {
+    if (negate_f32(3.5f) != -3.5f) return 1;
+    if (negate_f64(-4.2) != 4.2) return 2;
+    return 0;
+}
+
+[expected_return_code]
+0