Add README for cairo verifier

stwo_cairo_verifier/README.md

@@ -0,0 +1,47 @@
+# Stwo Cairo Verifier
+
+A [Cairo](https://github.com/starkware-libs/cairo) program that verifies a Stwo proof.
+
+## Running tests
+
+[Install asdf](https://asdf-vm.com/guide/getting-started.html#_3-install-asdf).
+
+```bash
+scarb test
+```
+
+## Visualising test step counts.
+
+Modify [`Scarb.toml`](./Scarb.toml) to use [Starknet Foundary](https://github.com/foundry-rs/starknet-foundry).
+
+```diff
+[dev-dependencies]
+- cairo_test = "2.8.0"
++ snforge_std = { git = "https://github.com/foundry-rs/starknet-foundry", tag = "v0.32.0" }
++ assert_macros = "2.8.0"
++
++ [scripts]
++ test = "snforge test --max-n-steps 100000000"
+```
+
+Generate trace for all tests.
+
+> :warning: Get errors with this on Linux.
+
+```bash
+scarb test -- --save-trace-data
+```
+
+Install [cairo-profiler](https://github.com/software-mansion/cairo-profiler) and run:
+
+```bash
+# Replace `TEST_NAME` with the name of the test you want profiled.
+cairo-profiler ./snfoundry_trace/TEST_NAME.json
+```
+
+Visualise profile in the browser.
+
+```bash
+# Once opened navigate to `Sample -> steps`.
+go tool pprof -http=":8000" profile.pb.gz
+```