feature(update): update information and structure of network page

This MR introduces:

• add information about IPv6.
• add information about deallocation policies for FIPs.
• change structure of Network page.
• add padding to Table of contents.

content/cloud/network/index.md

@@ -35,7 +35,7 @@ The situation is rather different for group projects. You cannot use the same ap
 - `public-muni-147-251-255-GROUP`
 
 {{< hint danger >}}
-Addresses that are unused for longer than 6 months will be released.
+Addresses that are unassigned for longer than 3 months can be released.
 {{< /hint  >}}
 
 {{< hint info >}}