use/gettin_started.rst: talk more about hostmasks

Adding strict hostmask isn't the only option, you can use wildcards and
the most used wildcards are now explained.

* nick starts with specific way (nick*!ident@host)
    * server which has identd and bots with same ident
* any nick with specific ident (*!ident@host)
    * server which doesn't have bots, but has multiple users
* anything with specific host (*!*@host)
    * cloaks/vhosts