Display semver exempt APIs on docs.rs
diff --git a/Cargo.toml b/Cargo.toml
index f009016..21f8f69 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -17,6 +17,9 @@
 [lib]
 doctest = false
 
+[package.metadata.docs.rs]
+rustdoc-args = ["--cfg", "procmacro2_semver_exempt"]
+
 [dependencies]
 unicode-xid = "0.1"