`Site search` `Add` button needs better UI placement

[stephendonner]

Description

Site search Add button needs better UI placement

Steps to reproduce

1. install 1.69.62
2. launch Brave
3. open brave://settings/searchEngines
4. look at the Add button adjacent to the Site search heading

Actual result

It's too close to the by text, here:

Expected result

Better UI placement of the Add button for the Site Search section of brave://settings/searchEngines

Reproduces how often

Easily reproduced

Brave version (brave://version info)

Brave | 1.69.62 Chromium: 127.0.6533.17 (Official Build) nightly (64-bit)
-- | --
Revision | 50af8e07a47dfe29f581936e45c07e8ee8b676f5
OS | Windows 10 Version 22H2 (Build 19045.4598)

Channel information

• [X] release (stable)
• [X] beta
• [X] nightly

Reproducibility

• [X] with Brave Shields disabled
• [X] with Brave Rewards disabled
• [ ] in the latest version of Chrome

Miscellaneous information

cc @aguscruiz @rebron @emerick @brave/qa-team

[aguscruiz]

We should probably change the location to the bottom of the list, like how we do in other menues.

Figma: https://www.figma.com/design/IXNCYwXmMWaF6u7Pdv1pOW/Desktop-settings---Nala?node-id=560-28946&t=uPiqxAXJwKsCB9lJ-1

Don't mind the different visual style, it's part of the redesign that's not in scope yet, just the button placement