Document use of double-dash arguments with vapor

[Jeffrey-de-Bruijn]

vapor run serve --hostname=0.0.0.0 --port=29200
vapor run serve --bind=0.0.0.0:29200

Give "Input not recognized" error. Vapor expects

vapor run serve --hostname 0.0.0.0 --port 29200
vapor run serve --bind 0.0.0.0:29200

This flag syntax does not conform to the GNU convention which is expected in GNU/Linux.

Because the syntax cannot be changed, it should be documented in the documentation whenever double-dash arguments are available, such as here

[0xTim]

Where else should this be documented?