Make addFunds open adjacent to Preferences tab

[cezaraugusto]

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Ran git rebase -i to squash commits (if needed).

Fix #5913

Auditors: @bsclifton
/cc @mrose17

Test Plan:

• Set env var ADDFUNDS_URL to some page i.e. https://cubits.com
• Open Preferences, go to Payments
• Open any other page
• Go back to Preferences, hit 'Add Funds'
• On modal dialog, hit 'Fund with debit/credit'
• When the new page opens, ensure it follows Preferences tab page right after
• Close the page
• Active page should be Preferences again

[bsclifton]

Tested manually, works perfectly! Great job 😄