Add new tab page settings

[rebron]

Description

Create new setting 'New tab page shows' with drop down menu:
a) Dashboard with images
b) Homepage
c) Blank page

Related to: #960
and should show in the Get Started section

[petemill]

We actually need the browser implementation for this as well. As in there is no functionality at the moment for new tabs to open to a specified URL. I’m not sure how much of a priority this would be for our users? Especially since an extension could fulfill that need.

[rebron]

Carryover as a muon feature parity. Separating out from the other issue due to actually having the functionality available.

[rebron]

We should probably reconsider placement. I'd rather these settings be available on the new tab page where it's accessible and relevant than buried in Settings. cc: @karenkliu, @cezaraugusto

[eljuno]

+1s from Community https://community.brave.com/t/feature-request-empty-new-tab-page/39676?u=eljuno

https://community.brave.com/t/disable-dashboard/44299?u=eljuno

https://community.brave.com/t/new-tab-page-options/45847/3?u=eljuno

[cezaraugusto]

agree with @rebron. cc @karenkliu for ideas

[srirambv]

++ on @rebron's idea of having it in new tab itself