Role::Tiny role that provides "instance" method turning your object into
singleton.
NOTE: Subsequent calls to "instance" will return the singleton instance ignoring
any arguments. This is different from MooseX::Singleton which does not allow any
arguments.
WWW: https://metacpan.org/pod/MooX::Singleton
PR: 237109
Submitted by: Geoffroy Desvernay
Approved by: (one of the mentors)