Add some cargo bench benchmarks

CONTRIBUTING.md

@@ -34,3 +34,15 @@ To run the `cap-primitives` fuzzer, run:
 cargo +nightly fuzz run cap-primitives
 ```
 
+## Benchmarking
+
+There are several micro-benchmarks for the `cap-std` crate which stress-test
+specific API features. As micro-benchmarks, they aren't representative of
+real-world use, but they are useful for development of `cap-std`.
+
+To run the `cap-std` benchmarks, run:
+
+```
+cargo +nightly bench
+```
+

Cargo.toml

@@ -29,6 +29,7 @@ yanix = "0.19.0"
 rand = "0.7.3"
 cap-tempfile = { path = "cap-tempfile", version = "0.0.0" }
 cap-directories = { path = "cap-directories", version = "0.0.0" }
+tempfile = "3.1.0"
 
 [target.'cfg(not(windows))'.dev-dependencies]
 libc = "0.2.72"