Fix the format of file resulting from 'ctrl+s' to make it usable as scene files

[zenkale]

Describe the bug
The file that results when we press to save a scene,"ctrl+s" has a different format as compared to format of .scn files. That makes the resulting file unusable as a scene file.

To Reproduce
Steps to reproduce the behavior:

1. Go to any of the scenes
2. press ctrl+h
3. Change the extension of the .json file to .scn file
4. try to use it in webaverse by pasting in scenes folder

Expected behavior
The format should be same as the .scn files so that the exact scenes can be saved and be usable next time.

Screenshots

Format of file resulting from ctrl+s:

Format of our scn file:

[avaer]

Completely agree, I think the Ctrl-S format is just out of date.

[lalalune]

@avaer fixed
#3653