Add option "Don't ask this again" to popups

Dear Brave Developers

Although warning and info popups are useful, they become distractive and annoying when there is no option to hide them.

A clear example is the Speedreader popup that is shown every time a user changes to reader mode. It is too much intrusive. A user should have the option to ask not to see this message again if the user has already decided he doesn’t want to active automatic speedreader.

It would be really useful to have the option “Don’t show this again” in the popup.