Add more details about running tests

Author: loganek

test/README.md

@@ -1 +1,12 @@
-See https://github.com/WebAssembly/wasi-testsuite
+# Running tests
+The following command executes wasi-threads tests using wasmtime runtime (please note wasi-threads proposal is still in development in Wasmtime and requires [this change](https://github.com/bytecodealliance/wasmtime/pull/5484) to work).
+
+```bash
+git clone -b prod/testsuite-all https://github.com/WebAssembly/wasi-testsuite
+cd wasi-testsuite/
+TEST_RUNTIME_EXE="wasmtime --wasm-features=threads --wasi-modules=experimental-wasi-threads" python3 test-runner/wasi_test_runner.py \
+    -r adapters/wasmtime.sh \
+    -t tests/proposals/wasi-threads/
+```
+
+See https://github.com/WebAssembly/wasi-testsuite for details.