feat(docu): Enhance the documentation of the _readonly feature
<website-feature> enable readonly </website-feature>
-This feature enables a readonly root partition with dmverity, additionally a separate readonly /usr partition can also use dmverity.
-If only /usr should be readonly and use dmverity, take a look at the next chapter to find an example for how to setup the fstab.mod for that case.
+This feature enables a readonly root partition together with `dm-verity`. By using `dm-verity`, the integrity of a block device is checked against a hash tree. Consequently, this ensures files have not changed between reboots or during runtime otherwise the access to those files would fail. An OverlayFS for `/var` and `/etc` ensures, that the Operating System stays operational during runtime.
+
+More information about `dm-verity` can be found [here](https://www.kernel.org/doc/html/latest/admin-guide/device-mapper/verity.html).
+
+Additionally, a separate readonly `/usr` partition is configured to be used with `dm-verity`, too.
+
+If only `/usr` should be configured this way (readonly & dm-verity) without enabling this feature for the whole root parition, take a look at the next chapter to find an example for how to setup the [fstab.mod](https://github.com/gardenlinux/gardenlinux/blob/main/features/_readonly/fstab.mod) for this case.
---
Type: flag
Included Features: server
-#
-## dmverity only for /usr with writable root partition
-To only enable dmverity for /usr and have a writable root partition the fstab.mod must be adjusted accordingly. But keep in mind that
-/etc/veritytab, that is containing the hash for the partition, most likely is located on a writable partition and therefore easy to modify.
+## dm-verity only for /usr with writable root partition
+
+In order to only enable dm-verity for `/usr` and have a writable root partition the [fstab.mod](https://github.com/gardenlinux/gardenlinux/blob/main/features/_readonly/fstab.mod) must be adjusted accordingly. But keep in mind that `/etc/veritytab`, which is containing the hash for the partition, most likely is located on a writable partition and therefore easy to modify.
NOTE: The sed statement does not remove the root partition from the fstab!
