Educational: Add documentation section about software alternatives

[amotl]

Hi.

at [1], the project is growing a list of alternative pieces of software and services which can be recommended to be used instead of the offerings of the GAFAMs. We are sure there are already other similar and more comprehensive curated lists out there, like awesome-privacy by @pluja and contributors.

Maybe it would be worth to add another section or dedicated page to https://gafam.info/ about those kinds of resources?

With kind regards,
Andreas.

[1] https://github.com/gafam/www.gafam.info/blob/main/doc/notes.rst#software-and-infrastructure-alternatives

/cc @nickspaargaren