docs: expand the explanation for the `[unsafe]` fn tag

doc/docs.md

@@ -4043,12 +4043,28 @@ fn bar() {
 	foo() // will not be called if `-d debug` is not passed
 }
 
-// Calls to this function must be in unsafe{} blocks
+// Calls to following function must be in unsafe{} blocks.
+// Note that the code in the body of `risky_business()` will still be
+// checked, unless you also wrap it in `unsafe {}` blocks.
+// This is usefull, when you want to have an `[unsafe]` function that
+// has checks before/after a certain unsafe operation, that will still
+// benefit from V's safety features.
 [unsafe]
 fn risky_business() {
+	// code that will be checked, perhaps checking pre conditions
+	unsafe {
+		// code that *will not be* checked, like pointer arithmetic,
+		// accessing union fields, calling other `[unsafe]` fns, etc...
+		// Usually, it is a good idea to try minimizing code wrapped
+		// in unsafe{} as much as possible.
+		// See also [Memory-unsafe code](#memory-unsafe-code)
+	}
+	// code that will be checked, perhaps checking post conditions and/or
+	// keeping invariants
 }
 
-// V's autofree engine will not take care of memory management in this function
+// V's autofree engine will not take care of memory management in this function.
+// You will have the responsibility to free memory manually yourself in it.
 [manualfree]
 fn custom_allocations() {
 }