docs: add lua testing documentation (#10060)

Signed-off-by: Spazzy <brendankamp757@gmail.com>

docs/lua_tests.md

@@ -0,0 +1,19 @@
+# Lua Tests
+
+## Running the Lua Tests
+
+To run the Lua tests you can run the following from the root directory:
+
+```bash
+make lua-test
+```
+
+This command makes use of docker hence does not need any dependency
+installations besides docker
+
+## Where are the Lua Tests?
+
+Lua Tests can be found in the [rootfs/etc/nginx/lua/test](../rootfs/etc/nginx/lua/test) directory
+
+
+[1]: https://openresty.org/en/installation.html