Support writing Inf and NaN values as null, instead of returning an error.

[pavelxdd]

Hello, could you add a support of writing Inf and NaN values as null, maybe via a writer flag?

Currently a apply this patch for yyjson in my project to achieve this:

diff --git a/src/yyjson.c b/src/yyjson.c
index 6a571b5..dc973a3 100644
--- a/src/yyjson.c
+++ b/src/yyjson.c
@@ -5635,7 +5635,8 @@ static_noinline u8 *write_f64_raw(u8 *buf, u64 raw, bool allow_nan_and_inf) {
                 return buf + 3;
             }
         } else {
-            return NULL;
+            *(v32 *)&buf[0] = v32_make('n', 'u', 'l', 'l');
+            return buf + 4;
         }
     }
     
@@ -5779,7 +5780,8 @@ static_noinline u8 *write_f64_raw(u8 *buf, u64 raw, bool allow_nan_and_inf) {
                 return buf + 3;
             }
         } else {
-            return NULL;
+            *(v32 *)&buf[0] = v32_make('n', 'u', 'l', 'l');
+            return buf + 4;
         }
     }
 }

[ibireme]

This feature is really necessary.
Added to the master branch, try this flag: YYJSON_WRITE_INF_AND_NAN_AS_NULL.