sysutils/linux-miniconda-installer: Aid for installing and using miniconda

Conda, like pip and CRAN, is a popular system that allows non-root users to
install many binary software packages in their own directories. The system
includes a base "channel" (repository) as well as 3rd party community
channels, such as "bioconda". QC for community channels is generally below
that of the base channel and FreeBSD ports, but they provide users with a
convenient way to install software not yet available in FreeBSD ports.

Packages are available for Linux, MacOS, and Windows. Linux Conda packages
work about as well on FreeBSD as they do on CentOS, which is the basis of
FreeBSD's Linux compatibility tool set. However, Conda and its packages
require a complete Linux environment for full functionality.

Typical Conda users do not know how to configure this environment on FreeBSD.
Miniconda-installer ensures a proper environment for installing and using
Miniconda and the packages it provides.