Add skeleton metadata to exported files

[talmo]

Currently, when saving triangulations or reprojections, we don't store metadata about the skeleton (nodes and edges):

sleap-anipose/sleap_anipose/triangulation.py

Lines 189 to 218 in 948b1c2

	with h5py.File(fname, "w") as f:
	f.create_dataset(
	"tracks",
	data=points_3d,
	chunks=True,
	compression="gzip",
	compression_opts=1,
	)
	if type(p2d) == str:
	tracks_descriptor = (
	"Shape: (n_frames, n_tracks, n_nodes, 3). "
	f"In calibration camera order: {cam_order}, "
	f"In session camera order: {[x.name for x in track_order]}"
	)
	else:
	tracks_descriptor = (
	"Shape: (n_frames, n_tracks, n_nodes, 3). "
	f"In calibration camera order: {cam_order}."
	)
	f["tracks"].attrs["Description"] = tracks_descriptor
	if frames:
	f.create_dataset(
	"frames", data=frames, compression="gzip", compression_opts=1
	)
	f["frames"].attrs[
	"Description"
	] = "Range, inclusive to exclusive, of frames triangulated over."

This would be great to have as metadata for downstream use.