[nxc init] now can also use the nix flake templates

Add some cli args to use the templates instead of copying the folders in /examples:

nxc init -t [template]
# or
nxc init --template [template]

ex:

nxc init -t webserver

there is also a flag to either fetch the template locally. by default we fetch the template from the flake on master on gitlab.

to use the local templates:

nxc init -t websever --use-local-templates