Add support for naked functions

src/doc/reference.md

@@ -1905,6 +1905,8 @@ type int8_t = i8;
 - `should_panic` - indicates that this test function should panic, inverting the success condition.
 - `cold` - The function is unlikely to be executed, so optimize it (and calls
   to it) differently.
+- `naked` - The function utilizes a custom ABI or custom inline ASM that requires
+  epilogue and prologue to be skipped.
 
 ### Static-only attributes