Automatically label PRs related to the new x64 backend
- "cranelift/peepmatic/**"
- "cranelift/codegen/src/peepmatic.rs"
+"cranelift:area:x64":
+ - "cranelift/codegen/src/machinst/**"
+ - "cranelift/codegen/src/isa/x64/**"
+
"cranelift:docs":
- "cranelift/docs/**"
