add redis filter to the example readme

Author: DannyBen

examples/filters/README.md

@@ -13,7 +13,7 @@ $ bashly init
 $ bashly generate
 ```
 
-<!-- include: src/lib/filter_docker_running.sh -->
+<!-- include: src/lib/filter_docker_running.sh src/lib/filter_redis_running.sh -->
 
 ---
 
@@ -57,6 +57,16 @@ filter_docker_running() {
 
 ```
 
+## `src/lib/filter_redis_running.sh`
+
+```bash
+# This is just a sample filter designed to always fail
+filter_redis_running() {
+  echo "Redis must be running (fake)"
+}
+
+```
+
 
 ## Generated script output