better install procedure

grattoir/__init__.py

@@ -1,6 +1,7 @@
 from selenium.webdriver import firefox
 from fake_useragent import UserAgent
 from pathlib import Path
+import importlib
 import os
 
 
@@ -21,6 +22,15 @@ def tor_browser_binary_path():
     return None
 
 
+def install_har_export_trigger(driver):
+    with importlib.resources.path(
+        __package__ + ".assets",
+        "har_export_trigger-0.6.2resigned1.xpi",
+    ) as p:
+        driver.install_addon(p.as_uri()[7:])
+    return driver
+
+
 class Grattoir(object):
     def __enter__(self):
         self._driver = None
@@ -34,7 +44,7 @@ class Grattoir(object):
         o.profile = profile
         o.binary = binary
         self._driver = firefox.webdriver.WebDriver(options=o)
-        self._driver.install_addon("assets/har_export_trigger-0.6.2resigned1.xpi")
+        self._driver = install_har_export_trigger(self._driver)
         return self._driver
 
     def __exit__(self, exc_type, exc_value, exc_tb):