Convert FreeBSD page as is from ZoF repo

Signed-off-by: George Melikov <mail@gmelikov.ru>

docs/Getting Started/FreeBSD.rst

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+|img|
+
+OpenZFS is an advanced file system and volume manager which was
+originally developed for Solaris and is now maintained by the OpenZFS
+community.
+
+Official Resources
+==================
+
+-  `ZoF GitHub Site <https://zfsonfreebsd.github.io/ZoF/>`__
+-  `OpenZFS site <http://open-zfs.org/>`__
+-  `OpenZFS repo <https://github.com/openzfs/zfs>`__
+
+Installation on FreeBSD
+=======================
+
+OpenZFS is available in the FreeBSD ports tree as sysutils/openzfs and
+sysutils/openzfs-kmod. It can be installed on FreeBSD stable/12 or
+later.
+
+The ZFS utilities will be installed in /usr/local/sbin/, so make sure
+your PATH gets adjusted accordingly.
+
+To load the module at boot, put ``openzfs_load="YES"`` in
+/boot/loader.conf, and remove ``zfs_load="YES"`` if migrating a ZFS
+install.
+
+Beware that the FreeBSD boot loader does not allow booting from root
+pools with encryption active (even if it is not in use), so do not try
+encryption on a pool you boot from.
+
+Development on FreeBSD
+======================
+
+The following dependencies are required to build OpenZFS on FreeBSD:
+
+-  FreeBSD sources in /usr/src or elsewhere specified by SYSDIR in env
+-  Packages for build:
+   ::
+
+      pkg install \
+          autoconf \
+          automake \
+          autotools \
+          bash \
+          git \
+          gmake \
+
+-  Optional packages for build:
+   ::
+
+      pkg install python37 # or your preferred Python version
+
+-  Packages for checks and tests:
+   ::
+
+      pkg install \
+          base64 \
+          checkbashisms \
+          fio \
+          hs-ShellCheck \
+          ksh93 \
+          pamtester \
+          py37-flake8 \
+      python37 \
+          sudo
+
+   Your preferred python version may be substituted. The user for
+   running tests must have NOPASSWD sudo permission.
+
+To build and install:
+
+::
+
+   # as user
+   git clone https://github.com/openzfs/zfs
+   cd zfs
+   ./autogen.sh
+   ./configure
+   gmake -j$(sysctl -n hw.ncpu)
+   # as root
+   gmake install
+
+Though not required, ``WITHOUT_ZFS`` is a useful build option in FreeBSD
+to avoid building and installing the legacy zfs tools and kmod - see
+``src.conf(5)``.
+
+For rapid development it can be convenient to do a UFS install instead
+of ZFS when setting up the work environment. That way the module can be
+unloaded and loaded without rebooting.
+
+Contributing
+============
+
+Submit changes to the `openzfs/zfs <https://github.com/openzfs/zfs>`__
+repo.
+
+Issues
+======
+
+Issues can be reported via GitHub's `Issue
+Tracker <https://github.com/openzfs/zfs>`__.
+
+.. |img| image:: https://github.com/zfsonfreebsd/ZoF/raw/gh-pages/zof-logo.png