Add informations on tiff file structure

[Farkal]

Tiff structure are not easy to catch and the resource on the internet are not very clear. This lead to some issues while creating a lib to encode/decode tiff, geotiff and cog files.

So i created some schemes to help people understand how a tiff and bigtiff file is structured:

I think it could be added to the website doc.
I based this scheme on the following sources: http://bigtiff.org/ and https://www.fileformat.info/format/tiff/egff.htm

I joined the draw.io scheme so you are free to add other information (there is also extensions to help you edit this files inside vscode)
tiff_structure.drawio.tar.gz