docs: lkl: add basic lklfuse documentation

Can be converted to a man page via rst2man.
The empty lines in the OPTIONS section aren't ideal, but it's the
simplest way to get the rst2man output on separate lines.

Signed-off-by: David Disseldorp <ddiss@suse.de>

Documentation/lkl/lklfuse.rst

@@ -0,0 +1,46 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========
+ lklfuse
+=========
+
+-----------------------------------------
+access LKL mounted block devices via FUSE
+-----------------------------------------
+
+:Date: 2025-06-23
+:Manual section: 8
+
+SYNOPSIS
+========
+
+lklfuse block-device mountpoint [options]
+
+DESCRIPTION
+===========
+
+lklfuse uses the Linux Kernel Library (LKL) to mount a block-device or
+filesystem image, and provides access to the host system via FUSE.
+lklfuse can run as an unprivileged user-space process, while reusing entire
+Linux kernel filesystem driver implementations.
+
+Udev rules and systemd service files are available for automatically mounting
+USB storage devices via an unprivileged lklfuse sandbox; see 61-lklfuse.rules
+and lklfuse-mount@.service.
+
+OPTIONS
+=======
+
+-o log=<file>           log to <file>.
+
+-o type=fstype          mount with filesystem type <fstype>.
+
+-o mb=memory            allocate <memory> in MB for LKL (default: 64).
+
+-o part=parition        mount <partition>.
+
+-o ro                   open file read-only.
+
+-o opts=options         Linux kernel mount <options> (use \\ to escape , and =).
+
+See `lklfuse --help` for additional FUSE specific options.