Added SetJSONIndent to Encoder

[xackery]

This pretty prints encoded gltf, e.g.

{"buffers":[{"uri":"data:application/octet-stream;base64

turns to

{
	"buffers": [
		{
			"uri": "data:application/octet-stream;base64

just by setting e.g.

enc := gltf.NewEncoder(w)
enc.AsBinary = false
enc.SetIndent("", "\t") // <-- this line
err = enc.Encode(doc)

[qmuntal]

Good addition, thanks!

[qmuntal]

Can you add a test which roundtrips (encode-> decode -> compare) an indented gltf just to be sure that it does not break anything?

[xackery]

Can you add a test which roundtrips (encode-> decode -> compare) an indented gltf just to be sure that it does not break anything?

I added additional tests inside encode_test that at least cover the new code, I am unsure if you want even more testing? From what I can tell, encode testing is exclusive to encode_test, but I basically do encode/decode/compare with this new commit ... Let me know if this satisfies your ask

[qmuntal]

LGTM!