fix: properly read in file

Author: corneliusroemer

src/pango_aliasor/aliasor.py

@@ -10,7 +10,8 @@ def __init__(self, alias_file=None):
                 file = json.load(file)
 
         else:
-            file = json.load(alias_file)
+            with open(alias_file) as file:
+                file = json.load(file)
 
         self.alias_dict = {}
         for column in file.keys():