Allow users to choose which browser's bookmarks to load

[jjw24]

Is your feature request related to a problem? Please describe.

Allow users to choose which browser's bookmarks to load. Currently supported browsers are Firefox, Chromium Edge, Internet Explorer and Chrome.

This issue is transferred from jjw24/Wox#97

First request has been completed.

This issue is for the second request:
Choose which browser to search bookmarks

Describe the solution you'd like

An option in the form of check boxes to allow user to select one, two etc or all browsers' bookmarks. Current default is all browser's bookmarks.