Document default middleware

[qwertycho]

Add better documentation of the default middleware.

From this discussion:

'When looking at the documentation there is no mention of compression being enabled. Currently the only mention of default middleware is Create a middleware handlers array and use the existing middleware already implemented within Microsoft.Kiota.HttpClientLibrary that includes existing handlers like retry, redirect, and more.'

It would be better to fully document all the default middleware (especially the CompressionHandler) so it's easier for starters to know what a kiota client is doing.

[baywet]

Thanks for pointing this out. Put together #133