Document how to decompress only some attributes in LAZ

[wonder-sk]

I have learned it is possible to make laz-perf read only some attributes of a LAZ file, saving some CPU time when reading data. It would be useful to have some documentation / code sample how to actually do that...

[NeDKaM]

It seems that unlike original LASzip implementation, laz-perf high-level API does not allow selective decompression by design. If you are building the library yourself : you can add selection yourself by disabling some layer decompression code, by adding some logic or by making a new high-level API based on provided low-level components.

More generally I find quite unpleasant to deal with a LASzip 1.5 (that misses some orignal features) without the explicit knowlegde of why it is somewhat "better". Community has been missing proper LAZ documentation for a while now and is forced to deal with obscure (to say the least) specification, only to discover that second major implementation failed to document on its own design.