add 404 page to Help Site

[marcochavezf]

cc @michelle-thompson

Details

Fixed Issues

$ https://github.com/Expensify/Expensify/issues/216920

Tests

0. (you need ruby and bundler installed to do this, more info here)

1. Run:

   cd docs
   bundle install
   bundle exec jekyll serve

2. Navigate http://localhost:4000/blabla (a non-existent page) and verify the 404 page is displayed

QA Steps

Follow step 2 from the Test section

Screenshots

Web

Mobile Web

[michelle-thompson]

Looks good to me!

[techievivek]

Looks good to me, just tested this locally and it works like charm.

[OSBotify]

✋ This PR was not deployed to staging yet because QA is ongoing. It will be automatically deployed to staging after the next production release.

[mvtglobally]

@marcochavezf @techievivek Can you validate this internally or update the QA steps for Staging so we can run it

[marcochavezf]

Oops I forgot to update the QA tests with the correct URL, but it's working fine on the production env (https://help.expensify.com/):