feat: Update main.py to accept file path as command-line argument

src/main.py

@@ -1,10 +1,20 @@
+import sys
 from lexer import Lexer
 from parser import Parser
 from interpreter import Interpreter
 
 def main():
-    with open('../examples/variables.fem', 'r') as f:
-        text = f.read()
+    if len(sys.argv) < 2:
+        print("Usage: python3 main.py <femcode_file>")
+        sys.exit(1)
+
+    file_path = sys.argv[1]
+    try:
+        with open(file_path, 'r') as f:
+            text = f.read()
+    except FileNotFoundError:
+        print(f"Error: File not found: {file_path}")
+        sys.exit(1)
 
     lexer = Lexer(text)
     tokens = lexer.tokenize()