Locale redirection doesn't work with back button

[arctic-hen7]

Describe the bug
Right now, Perseus' locale detection system doesn't compensate for the fact that the user might press the back button in their browser after being redirected, in which case they'll be taken back to a completely blank page.

To Reproduce
Steps to reproduce the behavior:

1. Enable i18n in any Perseus app with the locale parameter to the define_app! macro.
2. Create an index page at /.
3. Go to / in a browser, observe the locale redirection.
4. Press the back button in your browser.
5. See a blank screen.

Expected behavior
The user's back button should skip the interim locale detection page, and not display a blank page.

Screenshots
If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

• Perseus Version: v0.3.0-beta.6
• Sycamore Version: v0.6.1
• OS: Ubuntu
• Browser: Firefox
• Browser Version: 93

Additional context
This is due to the use of .set_href() on window.location, when we should be using .replace(), which is documented on MDN here.