rename folder to prompt_evaluations and update README

prompt_evaluations/07_prompt_foo_custom_graders/count.py

@@ -0,0 +1,17 @@
+import re
+
+def get_assert(output, context):
+    topic = context["vars"]["topic"]
+    goal_count = int(context["vars"]["count"])
+    pattern = fr'(^|\s)\b{re.escape(topic)}\b'
+
+    actual_count = len(re.findall(pattern, output.lower()))
+
+    pass_result = goal_count == actual_count
+
+    result = {
+        "pass": pass_result,
+        "score": 1 if pass_result else 0,
+        "reason": f"Expected {topic} to appear {goal_count} times. Actual: {actual_count}",
+    }
+    return result