Export RateLimiterPlugin from cpex_rate_limiter package (#5)

Allow `from cpex_rate_limiter import RateLimiterPlugin` to work
without reaching into the submodule.

Signed-off-by: Jonathan Springer <jps@s390x.com>
Signed-off-by: lucarlig <luca.carlig@ibm.com>

Author: jonpspri

rate_limiter/cpex_rate_limiter/__init__.py

@@ -9,3 +9,7 @@
 and backends, including in-memory and Redis, for per-user, per-tenant, and/or
 per-tool rate limiting. See the plugin documentation for configuration details.
 """
+
+from cpex_rate_limiter.rate_limiter import RateLimiterPlugin
+
+__all__ = ["RateLimiterPlugin"]