Respect NO_COLOR environment variable to disable color output

src/main.c

@@ -588,6 +588,11 @@ int main(int argc, char* argv[]) {
         dumpopts |= JV_PRINT_COLOR;
     }
 #endif
+    if (dumpopts & JV_PRINT_COLOR) {
+      char *no_color = getenv("NO_COLOR");
+      if (no_color != NULL && no_color[0] != '\0')
+        dumpopts &= ~JV_PRINT_COLOR;
+    }
   }
 #endif
   if (options & SORTED_OUTPUT) dumpopts |= JV_PRINT_SORTED;