Update some documentation

CHANGELOG.md

@@ -1,3 +1,19 @@
+unreleased
+----------
+- Add default implementation for `RuleSet::conditional_rules`
+- impl RuleSet for `syscalls::Sysno` for easier ad-hoc rulesets
+- Use generics instead of impl Trait in public functions to allow turbofish usage
+
+0.4.0
+-----
+- Add landlock functionality
+  - Add `landlock_rules` to RuleSet trait and new `LandlockRule` type
+  - Add `landlock_only` method to SafetyContext
+  - In test code, use rustls only in musl to get wider environment coverage
+  - Added several ExtraSafeError variants for Landlock-related errors
+  - See methods in SystemIO for how to use Landlock
+  - Landlock is enabled with the V2 ABI, which was added in kernel 5.19
+
 0.3.0
 -----
 - Switch seccomp backend to seccompiler

user-guide.md

@@ -97,7 +97,18 @@ Seccomp, the underlying functionality provided by the kernel that extrasafe uses
 
 If you want to use syscalls that aren't included in any of the builtin rulesets, consider [filing an issue to request a new one!](https://github.com/boustrophedon/extrasafe/issues)
 
-In the meantime, you can create your own:
+`RuleSet` is implemented for the `Sysno` type directly, so if you just want to enable one or two syscalls, the simplest way to do so is:
+
+```rust
+extrasafe::SafetyContext::new()
+    .enable(syscalls::Sysno::reboot).unwrap()
+    .enable(syscalls::Sysno::sysinfo).unwrap()
+    .apply_to_current_thread().unwrap();
+```
+
+However, this doesn't work for conditional rules yet.
+
+In the meantime, you can create your own RuleSet:
 
 ```rust
 use extrasafe::*;