This module provides a type safe path append operation by distinguishing
paths between rooted paths and branches. Rooted paths are represented by the
Rooted PosixPath type and branches are represented by the Unrooted PosixPath
type. Rooted paths are paths that are attached to specific roots in the file
system. Rooted paths could be absolute or relative e.g. /usr/bin,
./local/bin, or .. Unrootedes are a paths that are not attached to a
specific root e.g. usr/bin, local/bin, or ../bin are branches.
This distinction provides a safe path append operation which cannot fail.
These types do not allow appending a rooted path to any other path. Only
branches can be appended.