Ignore buggy clippy::empty_docs lint

rust-lang/rust-clippy#12377

```
error: empty doc comment
  --> openrr-plugin/src/gen/proxy.rs:10:1
   |
10 | #[sabi_trait]
   | ^^^^^^^^^^^^^
   |
   = help: consider removing or filling it
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#empty_docs
   = note: `-D clippy::empty-docs` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::empty_docs)]`
   = note: this error originates in the attribute macro `sabi_trait` (in Nightly builds, run with -Z macro-backtrace for more info)
```

Author: taiki-e

openrr-plugin/src/lib.rs

@@ -1,5 +1,6 @@
 #![doc = include_str!("../README.md")]
 #![warn(missing_docs)]
+#![allow(clippy::empty_docs)] // https://github.com/rust-lang/rust-clippy/issues/12377
 
 mod proxy;