message: doc: update outdated information
  - Fix up links;
  - Drop _frequently updated_ warning, etc.
diff: This guide shows you how to use fscache-based EROFS nydus image service to launch docker containers with the fscache-enabled in-kernel erofs on-demand download feature.
  -**Please be careful**, currently, the user-space daemon only implements _the basic functionality_ and it's aimed to test the fscache on-demand kernel code as a real end-to-end workload for container use cases, so it may take more extra steps compared with existing well-done solutions. This guide can be _frequently updated_ due to the overall implementation changes, so please make sure that you're now referring to the latest document version.
  -
  ## Prepare the kernel
  -Be aware of using the fscache-enabled erofs linux kernel, it can be built with the following steps:
  +Be aware of using the fscache-enabled erofs kernel (Linux 5.19+), it can be built with the following steps:
  1. ``git clone git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git`` \
  or (mirror in china): ``git://kernel.source.codeaurora.cn/pub/scm/linux/kernel/git/xiang/erofs.git``
  @@ -37,7 +35,7 @@ CONFIG_EROFS_FS_ONDEMAND=y
  1. Make sure you have installed _rust 1.52.1_ version and golang.
  2. Check out the latest nydus source code with \
  -``git clone https://github.com/dragonflyoss/image-service.git -b fscache``
  +``git clone https://github.com/dragonflyoss/image-service.git``
  3. Build nydusd with \
  ``cargo build --target x86_64-unknown-linux-gnu --features=fusedev --release --target-dir target-fusedev --bin nydusd``
  @@ -56,7 +54,7 @@ make
  2. Get nydus snapshotter with erofs supported:
  ```shell
  # clone code
  - git clone https://github.com/imeoer/nydus-snapshotter.git -b erofs-with-fscache-support
  + git clone https://github.com/containerd/nydus-snapshotter.git
  # compile binary to ./bin/containerd-nydus-grpc
  cd nydus-snapshotter
  make
  @@ -83,7 +81,7 @@ make
  ./bin/containerd-nydus-grpc \
  --config-path /path/nydus-erofs-config.json \
  --daemon-mode shared \
  - --daemon-backend erofs \
  + --daemon-backend fscache \
  --log-level info \
  --root /var/lib/containerd/io.containerd.snapshotter.v1.nydus \
  --cache-dir /var/lib/nydus/cache \
  