sources: catch timeout error on page load

frontools/sources.py

@@ -30,9 +30,9 @@ class Browser:
     async def load_page(self, url: str) -> AsyncGenerator[Page, None]:
         page = await self._browser_context.new_page()
         await page.route("*", self._source.route)
-        await page.goto(url)
         for retry in range(0, 3):
             try:
+                await page.goto(url)
                 await page.wait_for_load_state("networkidle")
                 break
             except TimeoutError:
@@ -60,7 +60,7 @@ class Source(ABC):
     ) -> AsyncGenerator[Browser, None]:
         """Return a Playwright browser that will eventually get files from local cache"""
 
-        viewport: Optional[ViewportSize] = cast(
+        viewport: ViewportSize = cast(
             ViewportSize, None
         )  # Playwright typings are broken