feat: bookmark bar

[eli0shin]

This PR implements a bookmark bar in wexond. It can be opened via the settings page, the window menu under bookmarks, or with the shortcut CmdOrCtrl+Shift+B.

This PR also changes the behavior of setting the height of the page BrowserView. Due to the fact that the height of the toolbar is now dynamic, the toolbar height is measured and used as the offset. The Window also watches the height of the toolbar and adjusts the BrowserView height to reflect the correct height whenever the toolbar height changes.

In addition, this PR fixes several current issues with bookmarks:

• Ensures the folder displayed in the add-bookmark dialog is correct
• Ensures that the most recently added bookmark will have the greatest order value
• Ensures that when bookmarks are updated, their parent folder accurately reflects them as a child

There are still a couple of limitation with the implementation of bookmarks in wexond:

• Due to the use of native Menu for bookmark bar dropdowns the items in the dropdown cannot be right-clicked to open the context menu and delete/edit the item.
• Bookmarks still cannot be re-ordered.
• Given the fact that a bookmark's folder cannot be updated from the bookmarks page and bookmarks in folders cannot be edited from the bookmarks bar, a bookmark in a folder can only be removed from that folder by navigating to the bookmark's page and clicking the star icon. (This is a carry-over of the current behavior.)

Notes: Added bookmark bar.

[sentialx]

LGTM 👍