Improve Docs general issue

[CarloLucibello]

a list of the things in the docs that could be improve

• Need some examples of edge maps use and constructors both in the docstrings and in the page https://carlolucibello.github.io/Erdos.jl/maps/
• Basic Interface: split in paragraphs or in different pages and add some comments. Also an index would be of help
  https://carlolucibello.github.io/Erdos.jl/core/
• README: give some prominence to the possibility to work with networks
• add some IJulia examples