Add a way to add, remove, and go to bookmarks

[FlafyDev]

Bookmarks are useful for quickly saving your location in a book and going somewhere else without any risks.

The implementations:

• A new screen similar to the notes' screen.
• A way to press on the top right of the screen to add/remove a bookmark.
• New property in the BookSavedData for the bookmarks.
• The bookmarks will use the consistent location of the page they are were assigned to to save their location.

Problems

1. if the bookmark saves its inner location by node index, how'd we know which nodes are currently in the page to know whether or not to show the bookmark?

Pick on of two solutions:

• This can be solved by sending all of the visible nodes from the renderer to the reader app. But this requires to check each node whether is visible or not, which may take a lot of time!
• To get the node indexes between pages get the current page node index and the next page node index and the indexes between them are in the current page. This only works if the node indexes increase by the inner page they are located at, which I think is true.

Edge cases:

1. Two bookmarks on the same page after resize of font (or anything else that changes the number of inner pages)

In that case only show the bookmark once but keep in mind that

[sugarico]

almost ebook app using epubcfi to location the bookmark, highlight, what do you thing about apply epubcfi https://idpf.org/epub/linking/cfi/