fix get navItem object bug by Navigation.get(target) method.

[NameHitherto]

When I want to use the get(target: string) method in navigation.js to get the target navItem I encountered a bug, the method provides two means of querying based on the id or href attributes of the navItem, when I need to query based on the id I need to manually add the # character, while at this time the target is no longer equal to the id value of the target navItem. So I restore the target value after the determination is over:

epub.js/src/navigation.js

Line 90 in f09089c

if(target.indexOf("#") === 0) {

and before calling getByIndex:

epub.js/src/navigation.js

Line 96 in f09089c

return this.getByIndex(target, index, this.toc);